Add documentation of "change closed" error when using ssh review

The "change closed" error can also occur when trying to submit a
review label with the ssh review command onto a change that has
been closed (submitted and merged, or abandoned) or onto a patchset
that has been replaced by a newer patchset.

Add this in the documentation.

Change-Id: Ic26e28b085e5d52742f593f7c2ce216c50a9db20
1 file changed