Add @MichaelCheco to Shimless RMA watchlist

- This change also removes @gavindodd from the watchlist.

Change-Id: I5b4c07a5320a51dae00c6ef4bff8446ecaab5d48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3454022
Auto-Submit: Michael Checo <michaelcheco@google.com>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Commit-Queue: Jimmy Gong <jimmyxgong@chromium.org>
Cr-Commit-Position: refs/heads/main@{#969725}

WATCHLISTS

@@ -2775,7 +2775,7 @@
                 'mvanouwerkerk+watch-sharing@chromium.org'],
     'shimless_rma': ['zentaro+watch-shimless@chromium.org',
                      'jimmyxgong+watch-shimless@chromium.org',
-                     'gavindodd+watch-shimless@chromium.org'],
+                     'michaelcheco+watch-shimless@google.com'],
     'site_engagement': ['dominickn+watch-engagement@chromium.org'],
     'site_instance': ['ajwong+watch@chromium.org',
                       'alexmos+watch@chromium.org',