Remove redundant "By" in mod action messages

[teraa]

Actions other than (un)ban/timeout

Or maybe just append (By: user) part to the original IRC message instead of displaying 2 lines for same event?

[mattts1]

Yeah it does make sense just to append (By tera_) at the end of "This room is no longer in followers-only mode" instead of two separate messages, because it would be obvious at that point that tera_ used the command.