Fix clipping issued with ScrollArea

[Barugon]

Closes #2811.

This code causes incorrect clipping. It also uses incorrect indexing (1 - d instead of just d). With this code removed, I have not been able to find a case where the scroll area contents invade the scroll bar area.

Because this was asked about in the original PR (#2839), here is a simple project with embedded ScrollAreas. I cannot see any difference between this branch and master.
scroll_test.zip

[Barugon]

Here's a screenshot of a ComboBox showing a date and time where I use UI::set_min_width in order to keep it from wrapping when the scroll bar appears.

Using the master branch:

Using this branch:

[edit] BTW, it would be nice to be able to disable wrapping for SelectableLabel, like how it can be disabled for Label.

[juancampa]

This code also causes an issue when a ScrollArea::vertical() is rendered inside a menu.

The content is clipped horizontally to the hard-coded menu width when the scrollbar appears.

Removing the code seems to fix it as well.

Screen.Recording.2023-08-19.at.6.57.42.PM.mov

[Barugon]

There are a number of issues that it causes but I haven't discovered what it's supposed to fix.

[emilk]

The code was added here: https://github.com/emilk/egui/pull/2665/files

I wish I had added an example or test to justify it… I'm a bit scared of removing it now, but let's try it and see what pops up :)