This PR fixes two visual issues, that were caused by the fact that we
were always painting the horizontal scrollbar even if there is no
horizontal scrolling possible
Obscuring deleted lines when using the inline assistant:
https://github.com/user-attachments/assets/f8460c3f-403e-40a6-8622-65268ba2d875
Cutting off text even when horizontal scrolling is not possible:
https://github.com/user-attachments/assets/23c909f7-1c23-4693-8edc-40a2f089d4a8
This issue was only present in some themes (e.g. Nord, Catpuccin)
Closes#22716
Release Notes:
- Fixed an issue where horizontal scrollbars of editors would always be
painted (even if there is no horizontal scrolling to be done)