gr-diff-processor: remove unused resolve value

The groups array passed to resolve() is never used, the array is passed
to gr-diff-builder through two-way binding since:

* db881fa Asynchronous diff rendering

Change-Id: I1ff5c436bb6ef432c4b595cb073ee95a3f1d5656

polygerrit-ui/app/elements/diff/gr-diff-processor/gr-diff-processor.js

@@ -172,7 +172,7 @@
               }
               // If we are done, resolve the promise.
               if (state.chunkIndex >= chunks.length) {
-                resolve(this.groups);
+                resolve();
                 this._nextStepHandle = null;
                 return;
               }