[devtools] add devtools-frontend to gclient repo_path_map

devtools-frontend is missing from {gclient_config.repo_path_map}, causing the breakage:
https://ci.chromium.org/p/devtools-frontend/builders/ci/DevTools%20Linux/b8904354993541218352

This CL adds devtools-frontend to {gclient_config.repo_path_map}

R=tandrii@chromium.org
TBR=machenbach@chromium.org
CC=yangguo@chromium.org

Change-Id: I14cd8e9a9f05bdf16fa1b3c83f95de314418877e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1767977
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Auto-Submit: Tamer Tas <tmrts@chromium.org>

recipes/recipe_modules/gclient/config.py

@@ -449,3 +449,7 @@ def devtools(c):
   s.name = 'devtools'
   s.url = 'https://chromium.googlesource.com/devtools/devtools-frontend.git'
   c.got_revision_mapping['devtools'] = 'got_revision'
+  c.repo_path_map.update({
+      'https://chromium.googlesource.com/devtools/devtools-frontend': (
+          'devtools/devtools-frontend', 'HEAD'),
+  })