[release-branch.go1.11] doc: update docs.html with new tour import path

As of golang.org/cl/141857 the import path has changed from
golang.org/x/tour/gotour to golang.org/x/tour

Change-Id: Ib54ab2e50188ef66c8a5c45136babfa49ad6934a
Reviewed-on: https://go-review.googlesource.com/c/141917
Run-TryBot: Andrew Bonventre <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>
(cherry picked from commit 035f9e8)
Reviewed-on: https://go-review.googlesource.com/c/143617

Author: andybons

doc/docs.html

@@ -50,10 +50,10 @@ <h3 id="go_tour">
 online</a> or{{end}} install it locally with:
 </p>
 <pre>
-$ go get golang.org/x/tour/gotour
+$ go get golang.org/x/tour
 </pre>
 <p>
-This will place the <code>gotour</code> binary in your workspace's <code>bin</code> directory.
+This will place the <code>tour</code> binary in your workspace's <code>bin</code> directory.
 </p>
 
 <h3 id="code"><a href="code.html">How to write Go code</a></h3>