Fix !pypi replies

[Kaztral-ar]

Fixes an issue where the !pypi command does not reply to the message that the user is replying to.

This changes the command to use the same reply behavior as other commands like !learn and !resources.

Fixes #3542

[jb3]

Is this something we see people trying to do?

Worth noting the original issue was not yet approved because I don't think we figured out what the criteria should be for enabling this.

I'm happy to merge this but in future please check issues have the approved label to save yourself work if we decide not to accept a contribution, and also I don't want to set a precedent that every command must support replies unless we see it being used or people think it will genuinely be useful.