[stable22] Fix header popover in richworkspace

[TSI-kavitasonawane]

backport of #1821

[juliusknorr]

Could you please provide some details on what this fix does, ideally with some before/after screenshots.

[TSI-kavitasonawane]

Could you please provide some details on what this fix does, ideally with some before/after screenshots.
Summary
Previously the popover for the header in the file browser was cut off. Now instead of making the whole text editor scrollable, only the content is.
@juliushaertl I have referred below Pull request link to fix the issue. This issue is already fixed for version 23.

#1821

Before:

After:

[juliusknorr]

I've rebased the changes again and pushed to a new PR: #2003