Only let the invoking user delete module not found error messages

[n0Oo0Oo0b]

When !pypi is unable to find a package, an error is sent like so:

However, the trashcan reaction can be used by anyone to delete the message. This can be problematic as it can be intentional to show that a package with that name doesn't exist. I propose that only the user that invoked the command will be able to delete the error message. This will also make the behavior more consistent with other delete functionalities like !eval.

[wookie184]

As far as I can tell only the invoker and moderators should be able to delete it. It will however always auto-delete after a delay to clean up the channel.

This isn't done with eval because a error is a valid result. We could change it for pypi, but I think most errors would probably be because of a mistake by the person running the command.

[wookie184]

Closing this as I don't think there's anything that should be changed.