Update DevTools DEPS (trusted)

Rolling third_party/depot_tools: https://chromium.googlesource.com/chromium/tools/depot_tools/+log/7a0dbd2..6cf251b

Roll created at https://cr-buildbucket.appspot.com/build/8722631275000116369

Bug: none
Change-Id: Id4b6e307e849ad378651d22683aa6eafc891254d
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6275317
Commit-Queue: Devtools Autoroller <devtools-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Devtools Autoroller <devtools-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>

Author: devtools-ci-autoroll-builder

DEPS

@@ -18,7 +18,7 @@ vars = {
   'buildtools_revision': 'f6b9b8d65b89dd04cd4937dfbef4a32fc6ddabe5',
 
   'depot_tools_url': 'https://chromium.googlesource.com/chromium/tools/depot_tools.git',
-  'depot_tools_revision': '7a0dbd20744917e3124a36276ef039848c4229ed',
+  'depot_tools_revision': '6cf251b5179f2cd5157cc314b60ef461d863eca1',
 
   'inspector_protocol_url': 'https://chromium.googlesource.com/deps/inspector_protocol',
   'inspector_protocol_revision': '940abfc668be2591483f7132145593c6a047f3cf',