Fix representation

It might be just me, but with `unless` it sounds like **if you want to use your forms in multiple places you should define it in your controllers**.


| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3
| Fixed tickets |
Then it becomes a bit unclear where "that" is refering too. What about: "The Form component allows you to build forms right inside your controller code, which is perfectly fine if you don't need to reuse the form somewhere else."