Various doc fixes for comp.el and comp.c

Various doc fixes for comp.el and comp.c

* lisp/emacs-lisp/comp.el: Remove redundant :group args.
(comp-async-cu-done-hook, comp-async-all-done-hook)
(comp-async-env-modifier-form, comp-dry-run)
(comp-ensure-native-compiler, comp-func-ret-typeset)
(comp-func-ret-range, comp-limple-lock-keywords)
(comp-make-curr-block):
* src/comp.c (Fcomp_el_to_eln_filename, Fcomp__init_ctxt)
(Fcomp_native_driver_options_effective_p)
(Fcomp__compile_ctxt_to_file, Fcomp_libgccjit_version)
(Fcomp__register_lambda, Fcomp__register_subr)
(Fcomp__late_register_subr, Fnative_elisp_load, syms_of_comp): Doc fixes.