Remove link in collapsed project sidebar top menu item

What does this MR do?

In the project sidebar, when the sidebar is collapsed and we hover one menu, we display a submenu like the following:

That first item Repository is clickable and we want to remove that option and make it not clickable.

In this MR we're removing the a tag in that element. In a following MR we will fix the styles of that first item.

Screenshots (strongly suggested)

Once the MR is applied, when the feature flag (sidebar_refactor) is disabled it's displayed like:

When the feature flag is enabled it shows like this:

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 properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Related to #42675 (closed)