doc/code.html: remove doubled word; modify the tab to space.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/8919043

doc/code.html

@@ -528,7 +528,7 @@ fetch and behaves the same as <code>go install</code>.)
 
 <p>
 After issuing the above <code>go get</code> command, the workspace directory
-tree should now now look like this:
+tree should now look like this:
 </p>
 
 <pre>