doc: fix a sentence position.

Only a last sentence of A Tour of Go is shifting to the left.
I fixed a HTML tag order according to other sentences it.

Change-Id: I6a301178d15db893f596b8da80a4d98721160386
Reviewed-on: https://go-review.googlesource.com/79856Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/docs.html

@@ -49,10 +49,10 @@ Each section concludes with a few exercises so you can practice what you've
 learned. You can {{if not $.GoogleCN}}<a href="//tour.golang.org/">take the tour
 online</a> or{{end}} install it locally with:
 </p>
-<p>
 <pre>
 $ go get golang.org/x/tour/gotour
 </pre>
+<p>
 This will place the <code>gotour</code> binary in your workspace's <code>bin</code> directory.
 </p>