encoding/json: adjust comment about encoding \b and \f
The encoding for the control characters \b and \f was
changed in http://go.dev/cl/521675. This CL adjusts the
corresponding comment about encoding bytes < 0x20.
Change-Id: I83b7311e4fa0731f6601ca64a66042425b4cecac
Reviewed-on: https://go-review.googlesource.com/c/go/+/523435 Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Joseph Tsai <joetsai@digital-static.net>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Joseph Tsai <joetsai@digital-static.net>