[test] adding header to fix warning

test/test_expand.c

@@ -4,6 +4,7 @@
 #include <stdarg.h>
 
 #include "greatest.h"
+#include "../src/string_utils.h"
 #include "../src/libpostal.h"
 
 SUITE(libpostal_expansion_tests);
@@ -168,7 +169,6 @@ TEST test_street_root_expansions(void) {
     PASS();
 }
 
-
 TEST test_expansions_language_classifier(void) {
     libpostal_normalize_options_t options = libpostal_get_default_options();