Replace nonexistent "withPHIDs()" in ChangesetQuery with "withIDs()"

Summary:
Ref T13519. See https://discourse.phabricator-community.org/t/error-call-to-undefined-method-differentialchangesetquery-withphids/3816/.

Changesets do not have PHIDs, and the Query has no "withPHIDs()" method. The keys in the viewstate storage are (usually) IDs.

Test Plan:

• On a revision with Diff 1 and Diff 2 affecting the same file:
  • Viewed Diff 1.
  • Hid file A.
  • Viewed Diff 2.
• Before patch: exception about call to "withPHIDs()", which does not exist for ChangesetQuery.
• After patch: no exception. Also, file actually unhid, which is the correct behavior!

Maniphest Tasks: T13519

Differential Revision: https://secure.phabricator.com/D21189