[xml] enum parameters in <commands> without group attribute

There are 180 of these:
[enum_without_group.txt](https://github.com/KhronosGroup/OpenGL-Registry/files/7552073/enum_without_group.txt)
P.S. This might become outdated again, here is an [auto-updating version](https://github.com/SunSerega/POCGL/blob/unstable/DataScraping/XML/GL/enum_without_group.txt).
(I only counted parameters with `GLenum` or `GLbitfield` type)

I'm not entirely sure if it's worth fixing, with its scale. Because it can't really be fully automated, someone needs to check every function individually.

But I guess it should be at least documented, that you can't rely on the `group` attribute being there...