Revert "Don't consider strings with variables to be static"

Summary:
Fixes T8379. This is causing some issues with linter rules so maybe this should just wait until T8049.

This reverts commit a9e581f6488fd7db83d4c02edee64db9b1cd3ef9.

Test Plan: N/A

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8379

Differential Revision: https://secure.phabricator.com/D13113