Fix ref encoding issue

What does this MR do and why?

When viewing a repository branch containing a special character in the branch name, the commit data was not being loaded correctly.

The reason for this was that the ref was not being encoded.

Screenshots or screen recordings

How to set up and validate locally

1. Create a branch containing a special character in the name
2. Select the branch in the ref switcher
3. The Files an commit data should be loaded as expected

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #385038 (closed)