R1:fceb9a3f9e1d

Hide the "Author" field in Differential on the web create workflow

Summary:
Ref T13628. When creating a revision, hide the recently introduced "Author" field.

It seems exceedingly unlikely that anyone would ever want to adjust this field when creating a revision, and this workflow already has a lot of fields and complexity, so this likely adds more noise than signal on the balance.

Test Plan:
- Created revisions via copy/paste on the web workflow, no longer saw "Author".
- Used "Edit Revision" to…