Use cancel-in-progress instead of styfle/cancel-workflow-action.

Compare cl/943495905 / google/guava#8542.

RELNOTES=n/a
PiperOrigin-RevId: 947083935

Author: cpovirk

.github/workflows/ci.yml

@@ -8,6 +8,11 @@ on:
     branches:
       - main
 
+# Cancel in-progress runs for pull requests, but not for master branch pushes
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   test:
     name: "JDK ${{ matrix.java }}"
@@ -16,11 +21,6 @@ jobs:
         java: [ 8, 11, 17 ]
     runs-on: ubuntu-latest
     steps:
-      # Cancel any previous runs for the same branch that are still running.
-      - name: 'Cancel previous runs'
-        uses: styfle/cancel-workflow-action@d07a454dad7609a92316b57b23c9ccfd4f59af66
-        with:
-          access_token: ${{ github.token }}
       - name: 'Check out repository'
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0
       - name: 'Cache local Maven repository'