Fix fsmonitor warning to not include global

The chromium build instructions for MacOS includes enabling `fsmonitor`
within the repository. With our warning message suggesting to disable it
globally, the fsmonitor still stays enabled within the repo. This CL
fixes this by disabling `fsmonitor` within the repository.

Change-Id: If261af8bc0d0a89bc193c178c8d5b5f80125d7b7
Fixed: 1476695
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4823891
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Auto-Submit: Aravind Vasudevan <aravindvasudev@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

git_common.py

@@ -426,7 +426,7 @@ def warn_submodule():
     print('WARNING: You have fsmonitor enabled. There is a major issue '
           'resulting in git diff-index returning wrong results. Please '
           'disable it by running:')
-    print('    git config --global core.fsmonitor false')
+    print('    git config core.fsmonitor false')
     print('We will remove this warning once https://crbug.com/1475405 is '
           'fixed.')
     print(colorama.Style.RESET_ALL)