R1:b93c2f68521d

Fix two Passphrase credential type issues

Summary:
Fixes T4991. Two issues:

- These error messages pass an object to "%s", when they mean to pass a type constant.
- The check for noncreatable credentials is incorrectly in the "edit" branch of the controller.

Test Plan:
- Edited a "SSH Key on disk" credential.
- Tried to create a credential with a bogus type.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T4991

Differential Revision: https…