cmd/go: fix 'go help mod edit' JSON documentation

The object representing a module directive may have a "Deprecated"
field but not a "Version" field. Other objects representing module
versions have "Path" and "Version" fields but not "Deprecated".

For #40357

Change-Id: Iad8063dfa6f7ceea22981a8a8f99e65fa3b7ffa0
Reviewed-on: https://go-review.googlesource.com/c/go/+/309337


Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>