remove unused FeedStory object in getTitleForFeed functions

Summary:
Removes an unused PhabricatorFeedStory Parameter from all getTitleForFeed() and getApplicationTransactionTitleForFeed() functions.
Ref D11088 Ref T6545

Test Plan: ran all unit tests and viewed some dashboard feeds

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6545

Differential Revision: https://secure.phabricator.com/D11146