Clarify the comment above chromite's DEPS pin.

Chromite is also used extensively throughout the OS-side of the world.
this comment should hopefully make it clear that chromium's pin of it
only affects chrome things.

Bug: None
Change-Id: I721ef80050cde8a5f76d318aec0cde9a94b42201
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377236Reviewed-by: Erik Chen <erikchen@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801889}

DEPS

@@ -873,7 +873,8 @@ deps = {
       'dep_type': 'cipd',
   },
 
-  # Build tools for Chrome OS.
+  # Tools used when building Chrome for Chrome OS. This affects both the Simple
+  # Chrome workflow, as well as the chromeos-chrome ebuild.
   'src/third_party/chromite': {
       'url': Var('chromium_git') + '/chromiumos/chromite.git' + '@' + '09ec5ae5729e3938a5e66e5976c61a5ef5757346',
       'condition': 'checkout_chromeos',