StreamCommand should not be restricted to a stream

[ehuss]

In #2049 it looks like commands that are addressed to triagebot are now restricted to be sent on a stream. This breaks usage of some commands like docs-update (and maybe ping-goals) which were intended to be mostly used in DMs. Can this functionality please be restored?

[Kobzol]

Right, I was wondering whether these commands were really supposed to be used on streams. Does it ever make sense to run docs-update or ping-goals in a stream? If not, I would just turn them into DM commands, which would make it easier.

[ehuss]

I kinda wanted to have the ability to run commands publicly so that others can see the interaction.

I think Niko has been using it the same way for ping-goals.

[Kobzol]

Ok, no problem, I will add them both as DM commands and reuse the logic.