runtime: make command name for &iskeywordprg more unique (#13297)

See https://github.com/vim/vim/pull/13213/commits by @dkearns:
Rename 'keywordprg' user command to ShKeywordPrg as this is just a
leaking implementation detail.

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/gpg.vim b/runtime/ftplugin/gpg.vim
index 2415555..7fb4f47 100644
--- a/runtime/ftplugin/gpg.vim
+++ b/runtime/ftplugin/gpg.vim
@@ -1,7 +1,7 @@
 " Vim filetype plugin file
 " Language:             gpg(1) configuration file
 " Previous Maintainer:  Nikolai Weibull <now@bitwi.se>
-" Latest Revision:      2008-07-09
+" Latest Revision:      2023-10-07
 
 if exists("b:did_ftplugin")
   finish
@@ -17,17 +17,17 @@
 
 if has('unix') && executable('less')
   if !has('gui_running')
-    command -buffer -nargs=1 Sman
+    command -buffer -nargs=1 GpgKeywordPrg
           \ silent exe '!' . 'LESS= MANPAGER="less --pattern=''^\s+--' . <q-args> . '\b'' --hilite-search" man ' . 'gpg' |
           \ redraw!
   elseif has('terminal')
-    command -buffer -nargs=1 Sman
+    command -buffer -nargs=1 GpgKeywordPrg
           \ silent exe ':term ' . 'env LESS= MANPAGER="less --pattern=''' . escape('^\s+--' . <q-args> . '\b', '\') . ''' --hilite-search" man ' . 'gpg'
   endif
-  if exists(':Sman') == 2
+  if exists(':GpgKeywordPrg') == 2
     setlocal iskeyword+=-
-    setlocal keywordprg=:Sman
-    let b:undo_ftplugin .= '| setlocal keywordprg< iskeyword< | sil! delc -buffer Sman'
+    setlocal keywordprg=:GpgKeywordPrg
+    let b:undo_ftplugin .= '| setlocal keywordprg< iskeyword< | sil! delc -buffer GpgKeywordPrg'
   endif
 endif