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
1 file changed