Replace 'DELETE' with 'REMOVE' for removing reviewers

The allowed backend action for removing a reviewer is 'REMOVE', hence
changing the frontend to use 'REMOVE' instead of 'DELETE'.

https://gerrit.googlesource.com/plugins/reviewers/+/
66ccd2f3dd2f6bb3272d4ccebcefa56e2fd49d49/src/main/java/com/googlesource/
gerrit/plugins/reviewers/PutReviewers.java#62

Change-Id: Ic9330eea5f7988d9066ab2a8ae94a93f8fc08881

rv-reviewers/rv-filter-section.js

diff --git a/rv-reviewers/rv-filter-section.js b/rv-reviewers/rv-filter-section.js
index 3bf6d06..fab5420 100644
--- a/rv-reviewers/rv-filter-section.js
+++ b/rv-reviewers/rv-filter-section.js
@@ -83,7 +83,7 @@
     } else {
       const index = e.model.index;
       const deleted = this.reviewers[index];
-      this._putReviewer(deleted, 'DELETE');
+      this._putReviewer(deleted, 'REMOVE');
     }
   }