Fix tracing of recordDirtyKeys

[pepeiborra]

I misunderstood how OpenTelemetry.Eventlog.addEvent works, which is not totally surprising since there are no docs.

But it looks like, judging by other call sites, that the event goes in the second argument and the first argument is always "":

haskell-language-server/ghcide/src/Development/IDE/Core/Tracing.hs

Line 123 in 7794398

liftIO $ withSpan (fromString name) (\sp -> addEvent sp "" (fromString $ name <> " received") >> runInIO (act sp))

[Anton-Latukha]

"" argument leads to: https://hackage.haskell.org/package/opentelemetry-0.7.0/docs/src/OpenTelemetry.Eventlog_Internal.html#local-6989586621679057309
It is k there.

So it is a prefix/part of the message monoid.

There are is a minor cleaned-up detail (withEventTrace :: ... no longer needs CPP), but that is a self-solving later refactoring detail.

Seems trivial enough to be approved by me.