GHA: Use 'gradle/actions/setup-gradle' to cache downloaded stuff

Change-Id: I7b3e72cf3d74ca84e25c7b5f8da89c8bed401591
Reviewed-on: https://review.couchbase.org/c/couchbase-elasticsearch-connector/+/235683
Reviewed-by: David Nault <[email protected]>
Tested-by: David Nault <[email protected]>

Author: dnault

.github/workflows/run-tests.yml

@@ -29,7 +29,9 @@ jobs:
         with:
           java-version: '21'
           distribution: 'temurin'
-          cache: 'gradle'
+
+      - name: Set up Gradle (for more sophisticated caching)
+        uses: gradle/actions/setup-gradle@v5
 
       - name: Run tests
         timeout-minutes: 60