Enable pipeline_editor_branch_switcher by default

What does this MR do?

This enables the pipeline_editor_branch_switcher feature flag by default.

Relevant Links

• Add the branch switcher to the pipeline editor
• Rollout pipeline_editor_branch_switcher

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)