fix(tests): skip query test on non-web platforms and remove obsolete timestamp_cursor_encoding_test

Author: SelaseKay

packages/cloud_firestore/cloud_firestore/example/integration_test/query_e2e.dart

@@ -1044,7 +1044,7 @@ void runQueryTests() {
             .get();
 
         expect(nextPage.docs, isEmpty);
-      });
+      }, skip: !kIsWeb);
 
       testWidgets(
         'throws exception without orderBy() on field used for inequality query',