Macro cleanup: Miscellaneous

These were found with -Wunused-macros. There are many more macros which
triggered that warning, but they were primarily part of larger sets of
macros so leave them alone.

src/nvim/syntax.c

@@ -223,8 +223,6 @@ struct name_list {
 #define ATTR_OFF (HL_ALL + 1)
 
 
-#define SYN_NAMELEN     50              /* maximum length of a syntax name */
-
 static char *(spo_name_tab[SPO_COUNT]) =
 {"ms=", "me=", "hs=", "he=", "rs=", "re=", "lc="};
 
@@ -6070,8 +6068,6 @@ do_highlight (
   int error = FALSE;
   int color;
   int is_normal_group = FALSE;                  /* "Normal" group */
-# define is_menu_group 0
-# define is_tooltip_group 0
 
   /*
    * If no argument, list current highlighting.