Redraw the Differential keyboard reticle after collapsing/un-collapsing an inline

Summary: Ref T12634. Fixes T10049. Toggling an inline currently leaves the reticle oddly-positioned.

Test Plan:

• Selected a comment with the keyboard.
• Collapsed it.
• Saw reticle behave reasonably.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12634, T10049

Differential Revision: https://secure.phabricator.com/D17903