"xwayland/glx: Enable sRGB fbconfigs" broke ~40% of VK-GL-CTS deqp_gles31

Unfortunately, !664 (merged) broke a lot (almost 40%) of tests in the VK-GL-CTS deqp_gles31 profile (both with llvmpipe and radeonsi on Navi 14).

Not sure it's directly related, but FWIW, the first GLX visual listed by glxinfo is marked as sRGB capable with it.

Shall we revert it for now and try again later?

(Might also be nice to add something to CI which could have caught this)