Ignore #hashtag implicit project tags which have no effect
Summary:
Fixes T5489. Currently, if you make a #proj comment on an object already tagged with #proj, you get a "no effect" dialog.
Instead, continue if these transactions produce no effect (this is normal/expected, and consistent with @user).
Test Plan: Made two #proj comments in a row on a revision.
Reviewers: joshuaspence, chad
Reviewed By: chad
Subscribers: epriestley
Maniphest Tasks: T5489
Differential Revision: https://secure.phabricator.com/D9745