runtime(vim): Update base-syntax, improve function definition matching

- Fix highlighting of function names including /fu\%[nction]/ (E.g.,
  s:func(), foo.fu(), fu.func())
- Match :delfunction argument.

Reported by Aliaksei Budavei.

closes: #17428

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/generator/gen_syntax_vim.vim

@@ -1,7 +1,7 @@
 " Vim syntax file generator
 " Language:		 Vim script
 " Maintainer:  Hirohito Higashi (h_east)
-" Last Change: 2025 Jun 01
+" Last Change: 2025 Jun 11
 
 let s:keepcpo= &cpo
 set cpo&vim
@@ -265,6 +265,7 @@ function s:get_vim_command_type(cmd_name)
 		debuggreedy
 		def
 		delcommand
+		delfunction
 		doautoall
 		doautocmd
 		echo