Blender Git Loki

UI: Use text highlight theme color for active tab

Currently, both inactive and active tabs are using the `Region Text` theme property.
This patch makes it so active tabs use `Region Text Highlight`.

Since this check is done in other places already but was simply missing in this case, I believe this was just an oversight and not a design decision.

Top is master, bottom is this patch:

{F11520838, size=full}

This allows this kind of tab highlight, not possible before since all tabs would have white text.

{F11520873, size=full}

Reviewed By: #user_interface, Severin

Differential Revision: https://developer.blender.org/D13003