Fix garden-o-matic link to last roll revision to point to the right revision.

BUG=271241
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/22309013

git-svn-id: svn://svn.chromium.org/blink/trunk@155914 bbb929c8-8fbe-4397-9dbb-9b2b20218538