Remove tests for JX.$.NotFound from Phabricator

Summary: See D939. Regardless of what we do there, these will break, and they're
pretty silly anyway (see the giant caveat comments in the second one).

Test Plan: Clicked a direct-jump comment link, did save/cancel for inline
comments.

Reviewers: phil, cpojer, tomo, mroch

Reviewed By: phil

CC: aran, phil

Differential Revision: 940