bpf: Remove local kptr references in documentation

We don't want to commit to a specific name for these. Simply call them
allocated objects coming from bpf_obj_new, which is completely clear in
itself.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221114191547.1694267-2-memxor@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>