Fix build with Qt 5.11_beta3 (dropping qt5_use_modules)
Summary:
A change in Qt 5.11_beta3 leads to errors like:
CMake Error at renderer/CMakeLists.txt:12 (qt5_use_modules):
`Unknown CMake command "qt5_use_modules".`
Test Plan: Built fine.
Reviewers: Kdenlive, mardelle
Reviewed By: Kdenlive, mardelle
Differential Revision: https://phabricator.kde.org/D12184