docs(lua): vim.keymap.set takes no noremap #37723

Problem: Unlike `nvim_keymap_set`, `vim.keymap.set` uses the non-negated
`remap` instead of `:set`'s `noremap`, but the documentation for this
got lost sometime before Nvim 0.10.

Solution: Restore the lost documentation and make it more explicit.

runtime/lua/vim/keymap.lua

@@ -3,6 +3,7 @@ local keymap = {}
 --- Table of |:map-arguments|.
 --- Same as |nvim_set_keymap()| {opts}, except:
 --- - {replace_keycodes} defaults to `true` if "expr" is `true`.
+--- - {noremap} is not supported; use {remap} instead (see below).
 ---
 --- Also accepts:
 --- @class vim.keymap.set.Opts : vim.api.keyset.keymap