Bump Java to 25 for besu builds

Match the teku bump so both JVM clients use the same JDK. Besu
still pins source/target compatibility to 21, but JDK 25 is
forward-compatible at compile time.

Author: claude

.github/actions/install-deps/action.yml

@@ -21,7 +21,7 @@ runs:
     if: contains(inputs.repository, 'besu')
     with:
       distribution: 'temurin'
-      java-version: '21'
+      java-version: '25'
   - uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
     if: contains(inputs.repository, 'lodestar') || contains(inputs.repository, 'ethereumjs')
     with: