chore: remove redundant postcode title and description overrides from controller

1. Removed duplicate postcode field definitions from WasteCollectionController.
2. These fields were already defined in PostcodeForm, making the controller definitions redundant.
3. Prevents potential conflicts or inconsistencies between form and controller logic.
4. Improves code clarity and adheres to DRY (Don't Repeat Yourself) principles.
5. No functional changes; only code cleanup for better maintainability.