chore: drop Bazel 5 testing

.github/workflows/ci.yaml

@@ -23,12 +23,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+      # TODO(alex): add testing on Bazel 7
       - id: bazel_6
         run: echo "bazelversion=$(head -n 1 .bazelversion)" >> $GITHUB_OUTPUT
-      - id: bazel_5
-        run: echo "bazelversion=5.3.2" >> $GITHUB_OUTPUT
     outputs:
-      # Will look like ["<version from .bazelversion>", "5.3.2"]
+      # Will look like ["<version from .bazelversion>", ...]
       bazelversions: ${{ toJSON(steps.*.outputs.bazelversion) }}
 
   matrix-prep-os:
@@ -72,13 +71,6 @@ jobs:
           - 'e2e/smoke'
           - 'e2e/worker'
         exclude:
-          # Don't test macos with Bazel 5 to minimize macOS minutes (billed at 10X)
-          # https://docs.github.com/en/billing/managing-billing-for-github-actions/about-billing-for-github-actions#included-storage-and-minutes
-          - os: macos-latest
-            bazelversion: 5.3.2
-          # Don't test bzlmod with Bazel 5 (not supported)
-          - bazelversion: 5.3.2
-            bzlmodEnabled: true
           # TODO
           - folder: e2e/loaders
             bzlmodEnabled: true