Add warning that patches should go to Gerrit instead of Bugzilla

Added "Note: Patches should go into Gerrit if possible." above
the checkbox asking if attachment is a patch on Bugzilla's attachment
page. (changed tab to 4 spaces to match rest of the code)

Bug: 42606
Change-Id: I4e5cfbed567d884a685740facd9becdd6841525c
Merge "Add warning that patches should go to Gerrit instead of Bugzilla"