runtime(vim): Update syntax file and syntax test (#13632)

Add missing assignment operators (:let*=, :let/= and :let%=).

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/vim.vim b/runtime/syntax/vim.vim
index a15a220..5eb3154 100644
--- a/runtime/syntax/vim.vim
+++ b/runtime/syntax/vim.vim
@@ -4,6 +4,7 @@
 " Last Change:	May 09, 2023
 " 	2023 Nov 12 by Vim Project (:let-heredoc improvements)
 " 	2023 Nov 20 by Vim Project (:loadkeymap improvements)
+" 	2023 Dec 06 by Vim Project (add missing :let{op}= assignment operators)
 " Version:	9.0-25
 " URL:	http://www.drchip.org/astronaut/vim/index.html#SYNTAX_VIM
 " Automatically generated keyword lists: {{{1
@@ -233,7 +234,7 @@
 " Operators: {{{2
 " =========
 syn cluster	vimOperGroup	contains=vimEnvvar,vimFunc,vimFuncVar,vimOper,vimOperParen,vimNumber,vimString,vimType,vimRegister,vimContinue,vim9Comment,vimVar
-syn match	vimOper	"||\|&&\|[-+.!]"				skipwhite nextgroup=vimString,vimSpecFile
+syn match	vimOper	"||\|&&\|[-+*/%.!]"				skipwhite nextgroup=vimString,vimSpecFile
 syn match	vimOper	"\%#=1\(==\|!=\|>=\|<=\|=\~\|!\~\|>\|<\|=\|!\~#\)[?#]\{0,2}"	skipwhite nextgroup=vimString,vimSpecFile
 syn match	vimOper	"\(\<is\|\<isnot\)[?#]\{0,2}\>"			skipwhite nextgroup=vimString,vimSpecFile
 syn region	vimOperParen 	matchgroup=vimParenSep	start="(" end=")" contains=vimoperStar,@vimOperGroup