Fix "Redundant specification of type arguments" warning

Change-Id: Ic8cfe9e27aa8eef1628fb7e84b2884974c34af2f
diff --git a/java/com/google/gerrit/server/util/RequestScopePropagator.java b/java/com/google/gerrit/server/util/RequestScopePropagator.java
index 10c46fc..e119e57 100644
--- a/java/com/google/gerrit/server/util/RequestScopePropagator.java
+++ b/java/com/google/gerrit/server/util/RequestScopePropagator.java
@@ -76,7 +76,7 @@
   public final <T> Callable<T> wrap(Callable<T> callable) {
     final RequestContext callerContext = requireNonNull(local.getContext());
     final Callable<T> wrapped = wrapImpl(context(callerContext, cleanup(callable)));
-    return new Callable<T>() {
+    return new Callable<>() {
       @Override
       public T call() throws Exception {
         if (callerContext == local.getContext()) {