This PR resolves a small regression introduced by the
debugger-introduction, which causes the active line number to no longer
be highlighted in the gutter as long as it is not part of a selection. A
user reported this issue [on
Discord](https://discord.com/channels/869392257814519848/995403703894954060/1357153291913662567).

Prior to the debugger-commit, an active line number was highlighted if
it was part of the editor active line numbers:

https://github.com/zed-industries/zed/blob/ed4e654fdf66fb886414198ac6db1a2f24d729a5/crates/editor/src/element.rs#L4295-L4303

With the debugger-introduction, the code was changed to only highlight
lines which are part of a selection:

https://github.com/zed-industries/zed/blob/e2aaf9b7046dd8d8430ff82554fe13d69431e443/crates/editor/src/element.rs#L2411-L2422

However, the check whether it is within a selection is not neccesary, as
the line is an active line as long as it is within the map of active
lines.

This PR restores the previous behavior.

| `main` | <img width="922" alt="main"
src="https://github.com/user-attachments/assets/486a548d-fe09-450e-922e-1feb4366fb4f"
/> |
| --- | --- |
| This PR | <img width="922" alt="PR"
src="https://github.com/user-attachments/assets/80517880-14b5-4861-bf83-8364f7831c46"
/> |

Release Notes:

- Fixed an issue where the active line number in the editor was not
always highlighted.