crypto/ssh: update references to the old code.google.com repo

Changed code.google.com repository links to the current
golang.org/x/crypto/ssh (except Gerrit homepage).

Change-Id: I7301d21401b163ceef8cfc1cf535dee998f9cb0d
Reviewed-on: https://go-review.googlesource.com/9250
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2 files changed