test(headline): update props count and list in headline test

- Decrease expected props length from 13 to 12
- Update props list to reflect the correct number of properties

Author: fulleni

test/src/models/entities/headline_test.dart

@@ -62,7 +62,7 @@ void main() {
       });
 
       test('props list should contain all relevant fields', () {
-        expect(headlineFixture.props.length, 13);
+        expect(headlineFixture.props.length, 12);
         expect(headlineFixture.props, [
           headlineFixture.id,
           headlineFixture.title,