bug#50005: 28.0.50; silence a couple byte-compiler warnings in ERC

[J.P.]

Mattias Engdegård <mattiase@acm.org> writes:

> The string made it look like backslash were a special character inside
> [...]. It isn't;

Thanks, and sorry you had to explain that. Sad as it is, I'm fairly
certain I even read as much in the Info manual only moments before
defiling that doc string:

  You cannot use ‘\’ to escape these three characters, since ‘\’ is not
  special here.

> Most ordinary uses of rx will not even require rx.el to be loaded at
> runtime since the macros are expanded during compilation

Again, thanks. Although I should know this instinctively by now, I too
often forget it when deep in the weeds.

> If you meant (in "a-c") in your first example then yes, quite right

Um, yeah, sure, let's go with that! ;)

> Wish I could but time probably doesn't permit, sorry.

Darn, well I definitely appreciate your insights on this one and the
effort made relating them (frustrating as that might have been).

> Of course I'll be happy to answer specifics about parts that I happen
> to know something about.

You may live to regret those words. (Thanks again.)