Read-only vs read only vs readonly

I had a customer point out to me that we're inconsistent in how we
spell read-only. Turns out we're not as inconsistent as I initially
thought :), but that they did manage to spot the one actual log
message we have that writes it differently than everything else -- but
that broke their grepping...

Almost everywhere we use read-only. Attached patch changes the one log
message where we didn't, as well as a few places in the docs for it. I
did not bother with things like comments in the code.

Two questions:

1. Is it worth fixing? Or just silly nitpicking?

2. What about translations? This string exists in translations --
should we just "fix" it there, without touching the translated string?
Or try to fix both? Or leave it for the translators who will get a
diff on it?

--
Magnus Hagander
Me: https://www.hagander.net/
Work: https://www.redpill-linpro.com/