CE-2971: Add git ref fallback for missing commit in git history

This simply adds a fallback in the JobGitRefLink component in the case of a missing commit in the git history.

We decided to remove the link and keep it as plain text in order to differentiate from normal commits that exist both in gitlab and git history.

Follow-up:

• Create a Review task of the JobsGitRefLink component as a whole, it's implementation and usage. while working on this ticket I felt like we are potentially doing unnecessary requests for data that we already receive from the `job` prop. There will probably also be some refactoring that could improve the components flexibility. However I felt like that was way outside the scope of this ticket so will create a follow-up Review ticket for this.

How it looks now

Individual job page:

Jobs page: