man: fix confusion in loader.conf

man: fix confusion in loader.conf

For some reason, the man page for loader.conf also mentioned type#1 entries
in passing. Except for using the same file extension, those files are in a
completely different format and with a different purpose. This mixup was
first introduced in f37d3835828c45b3a92ed12d9a6a30796c0a4a27, was then
reported in #10923, which was closed by cbae79b8d07327051c1e1f438f7086ab634b93f8,
but that didn't fix the actual issue.

Really fixes #10923.

While at it, simplify and improve the wording a bit.