Roll Media App from -wDCr73uu... to mqExY_CKG...

Release_Notes: http://go/media_app-x20/relnotes/Main/media_app_202101070600_RC00.html

https://chrome-infra-packages.appspot.com/p/chromeos_internal/apps/media_app/app/+/mqExY_CKGV64CkBK6pxd74QrlY0Ui90tdf5wIZPeB38C

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://skia-autoroll.corp.goog/r/media-app-chromium-autoroll
Please CC media-app@grotations.appspotmail.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Cq-Include-Trybots: luci.chrome.try:linux-chromeos-chrome
Bug: b/138961540
Tbr: media-app@grotations.appspotmail.com
Change-Id: Ic990ccda8d305951aa0089868c18f94dc848dacf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2614763Reviewed-by: chromium-internal-autoroll <chromium-internal-autoroll@skia-corp.google.com.iam.gserviceaccount.com>
Commit-Queue: chromium-internal-autoroll <chromium-internal-autoroll@skia-corp.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#841066}

DEPS

@@ -1609,7 +1609,7 @@ deps = {
     'packages': [
       {
         'package': 'chromeos_internal/apps/media_app/app',
-        'version': '-wDCr73uudKYVUOYqQJOHIYQHhh7Luoz49wve50i6eoC',
+        'version': 'mqExY_CKGV64CkBK6pxd74QrlY0Ui90tdf5wIZPeB38C',
       },
     ],
     'condition': 'checkout_chromeos and checkout_src_internal',