R1:15f14d6c2f20

Fix improper viewer for Git SSH cluster workflows

Summary: Ref T10751. These workflows have separate `getUser()` and `getViewer()` for weird legacy reasons. `getUser()` is correct.

Test Plan:
- Did a Git SSH push, verified that "Last Writer" reflected the proper user in the "Storage" UI in repository management.
- Grepped for other callsites, double-checked that they used correct users.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10751

Differential Revision: https://secure.phabricator.