multimedia/mpc-qt: drop unused OpenGL dependency
=>> Checking shared library dependencies
- 0x0000000000000001 NEEDED Shared library: [libGL.so.1] # 23.02
- 0x0000000000000001 NEEDED Shared library: [libGLX.so.0] # 23.12
- 0x0000000000000001 NEEDED Shared library: [libOpenGL.so.0] # 23.12
- 0x0000000000000001 NEEDED Shared library: [libQt6OpenGL.so.6] # 23.12