runtime(man): honor cmd modifiers before `g:ft_man_open_mode`

Give priority to (placement) command modifiers, specifically
`:vertical`, `:horizontal` and `:tab`, ahead of `g:ft_man_open_mode`,
so that if the user says e.g. `:vert Man`, Vim does the expected thing.

closes: #15117

Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/man.vim b/runtime/ftplugin/man.vim
index 87484bf..f0723ef 100644
--- a/runtime/ftplugin/man.vim
+++ b/runtime/ftplugin/man.vim
@@ -4,6 +4,7 @@
 " Maintainer:	SungHyun Nam <goweol@gmail.com>
 " Autoload Split: Bram Moolenaar
 " Last Change:	2024 Jun 06 (disabled the q mapping, #8210)
+" 		2024 Jul 06 (use nnoremap, #15130)
 
 " To make the ":Man" command available before editing a manual page, source
 " this script from your startup vimrc file.