Make few adjustments to [p]mywarnings and its docs

[Jackenmen]

Description of the changes

Look at the diff with "Hide whitespace changes" checked to see the changes more accurately.

In summary:

• fixed incorrect command in docs
• updated config call to not use the context manager since we don't intend to modify the data
• updated "You have no warnings" case to have a try-except for Forbidden on DM send and tick only after DM succeeds
• updated ctx.bot.send_interactive() call to pass user as channel directly instead of calling user.create_dm()
  • presumably this was done like that because there was a period of time when ctx.bot.send_interactive() had a bug that did not allow this
• removed unnecessary whitespace between description and newline

Have the changes in this PR been tested?

Yes