Remove mash_buildbot_filters from WATCHLISTS

These bots and filters don't exist any more.

Bug: none
Change-Id: Ic9a08c08b7459bde780689fac936453831b05275
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225150
Auto-Submit: James Cook <jamescook@chromium.org>
Commit-Queue: Michael Wasserman <msw@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773803}

WATCHLISTS

@@ -1203,9 +1203,6 @@
                   '|third_party/blink/(common|mojom)/manifest/'\
                   '|third_party/blink/renderer/modules/manifest/',
     },
-    'mash_buildbot_filters': {
-      'filepath': 'testing/buildbot/filters/mash.*filter',
-    },
     'media': {
       'filepath': 'media|third_party/(ffmpeg|opus|libvpx)'
     },
@@ -2559,8 +2556,6 @@
     'manifest': ['dominickn+watch-manifest@chromium.org',
                  'mlamouri+watch-manifest@chromium.org',
                  'dmurph+watching-manifest@chromium.org'],
-    'mash_buildbot_filters': ['dxie+watch@chromium.org',
-                              'jamescook+watch@chromium.org'],
     'media': ['feature-media-reviews@chromium.org'],
     'media_capture_from_element': ['emircan+watch+capturefromdom@chromium.org'],
     'media_controls': ['beccahughes+watch@chromium.org',