[x/tour] content: fix URLs in web service exercise
[x/tour] content: fix URLs in web service exercise

Update golang/go#13012

Change-Id: I62277ba3c8bcb57c8e8da5d00faec77c2a1ffa04
Reviewed-on: https://go-review.googlesource.com/17162
Reviewed-by: Katrina Owen <d322029bd4100ac9f2cfee3a363c04361456ec97@gmail.com>
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>
X-Tour-Commit: 14acca9afefff26fa3877acbc078674259763efd

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