fix(tests): Failing test on Mac

Don't know the root cause, but on Linux the values are not in list,
not checked the package versions yet, but this check doesn't make harm
It seems that this conversion happens implicitly somewhere

test/apps/_flask/__init__.py

@@ -71,7 +71,7 @@ def flaky():
     @app.route("/api/multipart", methods=["POST"])
     def multipart():
         files = {name: value.stream.read().decode() for name, value in request.files.items()}
-        return jsonify(**files, **request.form)
+        return jsonify(**files, **request.form.to_dict())
 
     @app.route("/api/teapot", methods=["POST"])
     def teapot():