Bump actions/checkout from 5 to 6 in the dependencies group

Bumps the dependencies group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `actions/checkout` from 5 to 6
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dependencies
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/api-breakage.yml

@@ -14,7 +14,7 @@ jobs:
       image: swift:latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
     # https://github.com/actions/checkout/issues/766

.github/workflows/ci.yml

@@ -56,7 +56,7 @@ jobs:
           POSTGRES_INITDB_ARGS: --auth-host=${{ matrix.postgres-auth }}
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: Test
       run: |
         swift test --enable-code-coverage

.github/workflows/nightly.yml

@@ -15,7 +15,7 @@ jobs:
       image: swiftlang/swift:${{ matrix.image }}
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: Test
       run: |
         swift test

.github/workflows/validate.yml

@@ -12,7 +12,7 @@ jobs:
     timeout-minutes: 15
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         fetch-depth: 1
     - name: run script

.github/workflows/verify-documentation.yml

@@ -17,12 +17,12 @@ jobs:
       run: |
         apt-get update && apt-get install -y rsync bc
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         path: "package"
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         repository: "hummingbird-project/hummingbird-docs"
         fetch-depth: 0