Roll SK Tool from c302f28e836a to 831c9fe9d89a

https://skia.googlesource.com/buildbot.git/+log/c302f28e836a..831c9fe9d89a

2021-05-24 kjlubick@google.com [infra] Reference main branch for docs/playbooks
2021-05-24 borenet@google.com [status] master -> main
2021-05-24 rmistry@google.com [docker_pushes_watcher] Fix Dockerfile
2021-05-24 rmistry@google.com Update +show references to master
2021-05-24 kjlubick@google.com [gold] Skip test that needs now() mocked
2021-05-24 borenet@google.com [sk] Fixes for release-branch

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/sk-tool-skia
Please CC kjlubick@google.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

Tbr: kjlubick@google.com
Change-Id: I55ed86caea78ec63981f70c51cc1dcd9c0ece3ba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/411751
Reviewed-by: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
diff --git a/DEPS b/DEPS
index 08ce2d3..653a4b9 100644
--- a/DEPS
+++ b/DEPS
@@ -6,7 +6,7 @@
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling different
   # dependencies without interference from each other.
-  'sk_tool_revision': 'git_revision:4ef22d867c8f8f60711b24635b724d75ec7377c6',
+  'sk_tool_revision': 'git_revision:831c9fe9d89a6212bccbf20c90d76176d5cf36b1',
 }
 
 deps = {