Update DevTools DEPS (trusted)

Rolling buildtools: https://chromium.googlesource.com/chromium/src/buildtools/+log/6767af3..7d7540c

Roll created at https://cr-buildbucket.appspot.com/build/8728486103660702961

Bug: none
Change-Id: I88083326d09e6831da529db637c76a812cdf85c9
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6088189
Bot-Commit: Devtools Autoroller <devtools-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Devtools Autoroller <devtools-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>

Author: devtools-ci-autoroll-builder

DEPS

@@ -15,7 +15,7 @@ vars = {
   'build_revision': '236b1807950d5ef2d472076a9a3b6dd45253139d',
 
   'buildtools_url': 'https://chromium.googlesource.com/chromium/src/buildtools.git',
-  'buildtools_revision': '6767af303e1d63fb618cf9d1a6591b4f83b92150',
+  'buildtools_revision': '7d7540c349fd6e5fc4b2241ee8aa3b17ed7261b6',
 
   'depot_tools_url': 'https://chromium.googlesource.com/chromium/tools/depot_tools.git',
   'depot_tools_revision': 'bf32de3167aa5d172223b50b13758f2fb0bce5e5',