Fix example command in READMe

[johnjoubert]

Update example command to rails generate noticed:notification instead of rails generate noticed:notifier

Pull Request

Summary:
The example command in the README on the main branch is incorrect. It should be rails generate noticed:notification NewCommentNotifier and not rails generate noticed:notifier NewCommentNotifier.

Checklist:

• Code follows the project's coding standards
• Tests have been added or updated to cover the changes
• Documentation has been updated (if applicable)
• All existing tests pass
• Conforms to the contributing guidelines

[excid3]

Good catch @johnjoubert 👍