Anyone can use the "set_mod_channel" command

[Autom3]

Describe the bug The check to see if someone is in fact a bot admin is done incorrectly

To Reproduce Steps to reproduce the behavior:

1. Open this link
2. As a non-bot admin, type !mod_channel in #botplayground
3. See that this error does not get printed

Expected behavior The error should be printed and the code should terminate at that line

Additional context The check currently checks if the function exists, rather than executing the function.

The faulty code has been copied by this pull request. So the issue needs to be fixed there as well.