Remove unused module requirement
Summary:
It was added for when FolderView did some low level GL stuff to fetch an
image for thumbnails, but now this uses higher level API.
Find -name CMakeLists.txt | xargs grep OpenGL returns nothing else
Test Plan:
Grepped for usages
Compiles fine
Reviewers: Plasma, mart
Reviewed By: Plasma, mart
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D9150