fix: changed redirect behavior with latest Flask versions

Author: ziirish

tests/legacy/test_api_legacy.py

@@ -375,7 +375,7 @@ def get(self):
 
         resp = client.get("/api")
         assert resp.status_code == 302
-        assert resp.headers["Location"] == "http://localhost/"
+        assert resp.headers["Location"] == "/"
 
     def test_calling_owns_endpoint_before_api_init(self):
         api = restx.Api()