docs: kdoc: trim __cacheline_group_* with the other annotations
The special case for __cacheline_group_begin/end() can be handled by just
adding another pattern to the struct_prefixes, eliminating the need for a
special case in push_parameter().
One change is that these annotations no longer appear in the rendered
output, just like all the other annotations that we clean out.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>