(partially) Fix Bug#55227 Fix compiler warnings in innodb with gcc 4.6

Fix compiler warning:
dict/dict0dict.c: In function 'dict_index_print_low':
dict/dict0dict.c:4444:14: error: variable 'type_string' set but not used [-Werror=unused-but-set-variable]

storage/innodb_plugin/dict/dict0dict.c

@@ -4441,7 +4441,6 @@ dict_index_print_low(
 {
 	ib_int64_t	n_vals;
 	ulint		i;
-	const char*	type_string;
 
 	ut_ad(mutex_own(&(dict_sys->mutex)));
 
@@ -4456,14 +4455,6 @@ dict_index_print_low(
 
 	dict_index_stat_mutex_exit(index);
 
-	if (dict_index_is_clust(index)) {
-		type_string = "clustered index";
-	} else if (dict_index_is_unique(index)) {
-		type_string = "unique index";
-	} else {
-		type_string = "secondary index";
-	}
-
 	fprintf(stderr,
 		"  INDEX: name %s, id %lu %lu, fields %lu/%lu,"
 		" uniq %lu, type %lu\n"