patch 9.0.0659: wrong type of comment in SetSyn() function

Problem:    Wrong type of comment in SetSyn() function.
Solution:   Use Vim9 comment. (closes #11278)

runtime/synmenu.vim

@@ -14,7 +14,7 @@ def SetSyn(name: string)
     filetype = "fvwm"
   endif
   if name == "whitespace"
-    " do not replace the filetype but add whitespace on top
+    # do not replace the filetype but add whitespace on top
     filetype = &ft .. ".whitespace"
   endif
   if !exists("s:syntax_menu_synonly")

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    659,
 /**/
     658,
 /**/