Matrix workflows refer to main branch (#3016)

Matrix workflows refer to main branch

### Motivation:

Now that the workflow files are committed we can refer to them on the
main branch

### Modifications:

Replace @matrix_file with @main

### Result:

More stable references in workflows.

.github/workflows/benchmarks.yml

@@ -70,7 +70,7 @@ jobs:
     name: Benchmarks
     needs: construct-matrix
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
     with:
       name: "Benchmarks"
       matrix_string: '${{ needs.construct-matrix.outputs.benchmarks-matrix }}'

.github/workflows/cxx_interop.yml

@@ -63,7 +63,7 @@ jobs:
     name: Cxx interop
     needs: construct-matrix
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
     with:
       name: "Cxx interop"
       matrix_string: '${{ needs.construct-matrix.outputs.cxx-interop-matrix }}'

.github/workflows/main.yml

@@ -10,7 +10,7 @@ jobs:
   unit-tests:
     name: Unit tests
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/unit_tests.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
     with:
       linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
       linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
@@ -21,12 +21,12 @@ jobs:
   cxx-interop:
     name: Cxx interop
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/cxx_interop.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/cxx_interop.yml@main
 
   benchmarks:
     name: Benchmarks
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/benchmarks.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/benchmarks.yml@main
     with:
       benchmark_package_path: "Benchmarks"
 
@@ -50,7 +50,7 @@ jobs:
     name: Integration tests
     needs: construct-integration-test-matrix
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
     with:
       name: "Integration tests"
       matrix_string: '${{ needs.construct-integration-test-matrix.outputs.integration-test-matrix }}'

.github/workflows/pull_request.yml

@@ -14,7 +14,7 @@ jobs:
   unit-tests:
     name: Unit tests
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/unit_tests.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
     with:
       linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
       linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
@@ -25,14 +25,14 @@ jobs:
   benchmarks:
     name: Benchmarks
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/benchmarks.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/benchmarks.yml@main
     with:
       benchmark_package_path: "Benchmarks"
 
   cxx-interop:
     name: Cxx interop
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/cxx_interop.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/cxx_interop.yml@main
 
   construct-integration-test-matrix:
     name: Construct integration test matrix
@@ -54,7 +54,7 @@ jobs:
     name: Integration tests
     needs: construct-integration-test-matrix
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
     with:
       name: "Integration tests"
       matrix_string: '${{ needs.construct-integration-test-matrix.outputs.integration-test-matrix }}'

.github/workflows/unit_tests.yml

@@ -106,7 +106,7 @@ jobs:
     name: Unit tests
     needs: construct-matrix
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@matrix_file  # TODO: replace with @main
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
     with:
       name: "Unit tests"
       matrix_string: '${{ needs.construct-matrix.outputs.unit-test-matrix }}'