patch 8.2.3930: getcmdline() argument has a misleading type

Problem:    getcmdline() argument has a misleading type.
Solution:   Use the correct type, even though the value is not used.

src/ex_getln.c

@@ -1554,10 +1554,10 @@ init_ccline(int firstc, int indent)
  */
     char_u *
 getcmdline(
-    int		firstc,
-    long	count,		// only used for incremental search
-    int		indent,		// indent for inside conditionals
-    int		do_concat UNUSED)
+    int		  firstc,
+    long	  count,	// only used for incremental search
+    int		  indent,	// indent for inside conditionals
+    getline_opt_T do_concat UNUSED)
 {
     return getcmdline_int(firstc, count, indent, TRUE);
 }