HOTFIX: Add 4.2 branch to CI (apache#20963)

Add 4.2 branch to CI, as discussed in
apache#20948 (review)

Reviewers: PoAn Yang <[email protected]>, Ken Huang
 <[email protected]>, Chia-Ping Tsai <[email protected]>

Author: Rancho-7

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ on:
   push:
     branches:
       - 'trunk'
-      - '4.0'
+      - '4.2'
 
   schedule:
     - cron: '0 0 * * 6,0'    # Run on Saturday and Sunday at midnight UTC
@@ -28,7 +28,7 @@ on:
     types: [ opened, synchronize, ready_for_review, reopened ]
     branches:
       - 'trunk'
-      - '4.0'
+      - '4.2'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}