find-duplicate-usernames.sh: add example output of git grep
find-duplicate-usernames.sh: add example output of git grep

Change-Id: Idf843d61577f9c01695f6b5996a1a935b0dedd41

GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit