[x/tour] go-tour: update sub-repo import path I missed the appengine one in last CL.
[x/tour] go-tour: update sub-repo import path
I missed the appengine one in last CL.

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/176670043
X-Tour-Commit: 3bf36a971d4d9830b33bd4198536e34dfba12246

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website