runtime(vim): Update base-syntax, fix escaping :syn and :hi sub-groups (#14137)

* runtime(vim): Update base-syntax, fix escaping :syn and :hi sub-groups

- Remove contained :syntax and :highlight sub-groups from the function
  body cluster.  These should only match in the respective commands.
- Remove vimSynLine syntax group from several clusters.  The definition
  of vimSynLine was removed in Vim 5.3.

* runtime(vim): Update syntax generator, use standard Last Change date format

The de facto standard date format is YYYY MMM DD.

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

runtime/syntax/generator/gen_syntax_vim.vim

@@ -2,7 +2,7 @@
 " Language: Vim script
 " Maintainer: Hirohito Higashi (h_east)
 " URL: https://github.com/vim-jp/syntax-vim-ex
-" Last Change: Mar 02, 2024
+" Last Change: 2024 Mar 02
 " Version: 2.0.4
 
 let s:keepcpo= &cpo