log/slog: fix comment above log levels

This extra newline causes pkg.go.dev and gopls to only show the bottom
half of this comment; I'm pretty sure this entire thing is meant to be
in the docs.

Change-Id: I5bbf081fb2072d9d773d5a995bc3693dc44f65ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/511855
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/log/slog/level.go

@@ -23,7 +23,6 @@ type Level int
 // First, we wanted the default level to be Info, Since Levels are ints, Info is
 // the default value for int, zero.
 //
-
 // Second, we wanted to make it easy to use levels to specify logger verbosity.
 // Since a larger level means a more severe event, a logger that accepts events
 // with smaller (or more negative) level means a more verbose logger. Logger