Remove hardcoded Go version

Author: dveeden

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       - name: setup go
         uses: actions/setup-go@v4
         with:
-          go-version: 1.21
+          go-version-file: 'mysql-tester/go.mod'
       - name: vet
         working-directory: 'mysql-tester'
         run: go vet ./...