vim-patch:3697c6b: runtime(ssh): ignore case in 'keywordprg', update syntax script (#38277)

- ftplugin(sshdconfig): use "-I" for 'keywordprg' to search
  case-insensitive in the man page
- syntax(sshdconfig,sshconfig): Mark "lowdelay", "throughput", and
  "reliability" as deprecated for IPQoS, highlighting them as
  errors/warnings to reflect OpenSSH 10.1p1 release

Reference:
https://www.openssh.org/releasenotes.html#10.1p1

closes: vim/vim#19636

3697c6b020

Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>

runtime/ftplugin/sshconfig.vim

@@ -2,7 +2,7 @@
 " Language:	OpenSSH client configuration file
 " Maintainer:	This runtime file is looking for a new maintainer.
 " Previous Maintainer:	Nikolai Weibull <now@bitwi.se>
-" Latest Revision:	2025-07-22 (use :hor term #17822)
+" Latest Revision:	2026-03-11 (`less -I`)
 
 if exists("b:did_ftplugin")
   finish
@@ -17,7 +17,7 @@ let b:undo_ftplugin = 'setlocal com< cms< fo<'
 
 if has('unix') && executable('less') && exists(':terminal') == 2
   command -buffer -nargs=1 SshconfigKeywordPrg
-        \ silent exe 'hor term ' . 'env LESS= MANPAGER="less --pattern=''' . escape('^\s+' . <q-args> . '$', '\') . ''' --hilite-search" man ' . 'ssh_config'
+        \ silent exe 'hor term ' . 'env LESS= MANPAGER="less -I --pattern=''' . escape('^\s+' . <q-args> . '$', '\') . ''' --hilite-search" man ' . 'ssh_config'
   setlocal iskeyword+=-
   setlocal keywordprg=:SshconfigKeywordPrg
   let b:undo_ftplugin .= '| setlocal keywordprg< iskeyword< | sil! delc -buffer SshconfigKeywordPrg'