GitHub CI: Replace obsolete gradle/wrapper-validation-action with setup-gradle action.

Hopefully this resolves the network issues that are causing that step to fail.
See gradle/actions#631
and https://github.com/gradle/actions

PiperOrigin-RevId: 802349321

Author: brettchabot

.github/workflows/ci.yml

@@ -87,8 +87,8 @@ jobs:
         with:
           distribution: 'zulu'
           java-version: '21'
-      - name: Gradle wrapper validation
-        uses: gradle/wrapper-validation-action@v2
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
       - name: Enable KVM group perms
         run: |
             echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' | sudo tee /etc/udev/rules.d/99-kvm4all.rules