lorder: add note that it is no longer required

Use of lorder(1) is not required by contemporary linkers.

The GNU coreutils manual[1] has a good description of the use of lorder
and tsort:

This whole procedure has been obsolete since about 1980, because
Unix archives now contain a symbol table (traditionally built by
ranlib, now generally built by ar itself), and the Unix linker uses
the symbol table to effectively make multiple passes over an archive
file.

See 0e1e341b486c for some more details.

[1] https://www.gnu.org/software/coreutils/manual/html_node/tsort-background.html

PR: 259254 [exp-run]
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation