Tutorial part 4, explicit list for reverse() args

[Julien Vallet]

The current version (​https://github.com/django/django/blob/main/docs/intro/tutorial04.txt#L106) is creating an implicit list by using a trailing comma. I suggest to use an explicit list instead to both be inline with the documentation and avoid user error/confusion.

I already have a pull request to address this issue (​https://github.com/django/django/pull/22246).