Straighten out some stacked action removal behaviors

Summary: Fixes T12065. Some of the normal behavior of these actions got juggled when I made "Accept" and "Reject" conflict.

Test Plan:

• Added "Accept".
• Added "Reject", saw it remove "Accept".
• Added "Change Projects".
• Added "Assign/Claim".
• Removed "Assign/Claim".
• Removed "Accept".

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12065

Differential Revision: https://secure.phabricator.com/D17143