Switch Branches and MR tab order in IDE

What does this MR do?

In the Web IDE nav dropdown, the order of the tabs does not match the order of information in the dropdown. Let's switch the MR and Branches tabs.

Screenshots

Before	After

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content