build: update samples/stylecheck to use java 11 to match new style guide as indicated in: https://github.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md#java-version (#3516)

This fixes the samples/stylecheck in PR#3487

Author: PhongChuong

.github/workflows/samples.yaml

@@ -24,7 +24,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 8
+          java-version: 11
       - name: Run checkstyle
         run: mvn -P lint --quiet --batch-mode checkstyle:check
         working-directory: samples/snippets