Migrate to actions@v3.

More information: https://github.com/actions/cache

Also, disabling g++-10 on macOS. Not clear which version is the default now.

PiperOrigin-RevId: 485072885

.github/workflows/linux-ci.yml

@@ -17,18 +17,10 @@ jobs:
       CXX: g++-10
 
     steps:
-    - uses: actions/checkout@v2
-
-    - name: Free up some space in an image
-      run: |
-        # This doesn't seem to affect the speed of the run, but takes ~2 minutes,
-        # commented out for now.
-        #sudo rm -rf /usr/share/dotnet
-        #sudo rm -rf /opt/ghc
-        df -h
+    - uses: actions/checkout@v3
 
     - name: Mount bazel cache
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         # See https://docs.bazel.build/versions/master/output_directories.html
         path: "~/.cache/bazel"

.github/workflows/macos-ci.yml

@@ -16,18 +16,18 @@ jobs:
     runs-on: macos-latest
     env:
       BAZEL: bazelisk-darwin-amd64
-      CC: gcc-10
-      CXX: g++-10
+      CC: gcc
+      CXX: g++
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Update environment variables
       run: |
         echo "USER=${USER}" >> ${GITHUB_ENV}
 
     - name: Mount bazel cache
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         # See https://docs.bazel.build/versions/master/output_directories.html
         path: /private/var/tmp/_bazel_${{ env.USER }}