runtime(help): fix end of sentence highlight in code examples

closes: #15745

Co-authored-by: Danilo Rezende <returndanilo@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/help.vim b/runtime/syntax/help.vim
index ff214e2..68f68c2 100644
--- a/runtime/syntax/help.vim
+++ b/runtime/syntax/help.vim
@@ -1,7 +1,7 @@
 " Vim syntax file
 " Language:	Vim help file
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2024 Oct 08
+" Last Change:	2024 Oct 16
 " Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 " Quit when a (custom) syntax file was already loaded
@@ -47,7 +47,8 @@
 syn match helpOption		"'t_..'"
 syn match helpNormal		"'ab'"
 syn match helpCommand		"`[^` \t]\+`"hs=s+1,he=e-1 contains=helpBacktick
-syn match helpCommand		"\(^\|[^a-z"[]\)\zs`[^`]\+`\ze\([^a-z\t."']\|$\)"hs=s+1,he=e-1 contains=helpBacktick
+" doesn't allow a . directly after an ending backtick. See :helpgrep `[^`,]\+ [^`,]\+`\.
+syn match helpCommand		"\(^\|[^a-z"[]\)\zs`[^`]\+`\ze\([^a-z\t."']\|[.?!]\?$\)"hs=s+1,he=e-1 contains=helpBacktick
 syn match helpHeader		"\s*\zs.\{-}\ze\s\=\~$" nextgroup=helpIgnore
 syn match helpGraphic		".* \ze`$" nextgroup=helpIgnore
 if has("conceal")