ci: bump deprecated actions/checkout and actions/cache to v4 in apidocs workflow

The build-javadoc-and-deploy job used actions/cache@v2 and actions/checkout@v2,
which are deprecated and now fail. Bump both to v4 to match ci.yml.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: rohanpadhye

.github/workflows/apidocs.yml

@@ -8,11 +8,11 @@ jobs:
   build-javadoc-and-deploy:
     runs-on: ubuntu-latest
     steps:
-      - name: Checkout latest # release or manually selected ref 
-        uses: actions/checkout@v2
+      - name: Checkout latest # release or manually selected ref
+        uses: actions/checkout@v4
 
       - name: Cache Maven dependencies
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/.m2/repository
           key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}