Revert "fix: MessageActionsBox: Fix message input scrolling out of view"

This reverts commit 9a68e96e.

There's is a chance that the adjustment values are changed during the paint phase. Adding or removing a CSS class in this period invalidates the current style, leading to a use after free.

See https://gitlab.gnome.org/GNOME/gtk/-/issues/7382 for more details.

Also, I cannot reproduce the original bug #12158 (closed) anymore. Edit: Indeed I still can, but it depends very much on the string entered. Just adding a few spaces somewhere isn't sufficient apparently.