Configure test-retry plugin filter properly

The intent of opensearch-project#8825 was to retry only specified tests. The wrong
parameter was configured though: ['filter' should be set][1], not
'classRetry'.

[1]: https://github.com/gradle/test-retry-gradle-plugin/blob/main/README.adoc#filtering

Signed-off-by: Andrew Ross <andrross@amazon.com>

build.gradle

@@ -470,7 +470,7 @@ subprojects {
         maxFailures = 10
       }
       failOnPassedAfterRetry = false
-      classRetry {
+      filter {
         includeClasses.add("org.opensearch.action.admin.cluster.node.tasks.ResourceAwareTasksTests")
         includeClasses.add("org.opensearch.action.admin.cluster.tasks.PendingTasksBlocksIT")
         includeClasses.add("org.opensearch.action.admin.indices.create.CreateIndexIT")