In case the qtcreator.ini has a TextEditor section without a defined
ColorScheme value, Qt Creator decides to create a new "styles/customized
%i.xml" and select that as scheme.
I assume that this was implemented way back then, as migration code when
selectable Color Schemes were introduced. These days, it makes
maintenance (and implementation of QTCREATORBUG-15229) more difficult.
Let's remove it.

Task-number: QTCREATORBUG-15649
Change-Id: I49102d02fa8e582a92f6e39faa8c7d3b58f531b3
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>