Clicking "Save and Continue" on the Branches page after already saving throws an error

[danielkberry]

When clicking "Save and Continue" on the Branches page after previously pressing "Save", a You are trying to swap branch names. Please choose another name for the branches. error is thrown.

Expected Behavior: The page is saved and progresses to the Metrics page.

Actual Behavior: An error is generated and the user remains on the Branches page.

https://github.com/mozilla/experimenter/assets/2738595/c13084c2-ceb5-4fe0-8a8b-bfa3375004d9

┆Issue is synchronized with this Jira Task