[colorcorrection] Make GammaRamp non-copyable
GammaRamp deletes an array in the destructor thus we have to either
declare our own copy constructor and copy assignment operator or
delete them both.
GammaRamp looks more like an identity rather than a value so both copy
constructor and copy assignment operator were deleted.
Test Plan: Compiles.
Reviewers: KWin, romangg
Reviewed By: KWin, romangg
Differential Revision: https://phabricator.kde.org/D16023