Use Java 25 for CI.

PiperOrigin-RevId: 897291410

Author: rluble

.github/workflows/ci.yaml

@@ -51,7 +51,7 @@ jobs:
       - name: Setup Java
         uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654  # v5.2.0
         with:
-          java-version: '21'
+          java-version: '25'
           distribution: 'zulu'
           java-package: jdk