zink: update textureCompressionBC requirement
The mesa state-tracker can now emulate all formats indicated by this
feature-flag, so we don't require this for OpenGL 4.2 any more.
It's however a good idea to support for power-usage and performance
reasons, saving on memory bandwidth. So let's move it to the
gl46_optimal block instead.
Fixes:
e4ff42684b9 ("mesa/st: enable bptc extension with fallback")
Fixes:
2ea481b2f0a ("Zink: add Zink profiles file")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19779>