In rare cases the requirement to have a Buganizer or Monorail bug ID
in the commit message can be unreasonable. For example when the build
is broken and the fix is trivial so the creation of a tracker bug would
needlessly take valuable time. Another example would be fixing a
spelling mistake in a comment and we don't want to spam the tracker
thread with a commit notification.

For such cases, accept bug info lines containing no digits.

Bug: b/141892461
Change-Id: Iaf44eb3dfc08d3e138fe8ba24501fa9c046d36de
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40029
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>