In the theme settings for the user interface, there was a option to
change the outline color of pulldown menus (E.g. the buttons at the top
of the 3D viewport) when the button was selected.
However this color wasn't used. This commit aims to fix that
by using the selected outline color for the outline of selected
pulldown buttons.
Pull Request: https://projects.blender.org/blender/blender/pulls/133470
be975efc9e