net/http: remove an errant space

Made the godoc overview section oddly indented
compared to the other code blocks.

R=golang-dev, mikioh.mikioh, dsymonds, r
CC=golang-dev
https://golang.org/cl/5645060

src/pkg/net/http/doc.go

@@ -12,7 +12,7 @@ Get, Head, Post, and PostForm make HTTP requests:
 	resp, err := http.Post("http://example.com/upload", "image/jpeg", &buf)
 	...
 	resp, err := http.PostForm("http://example.com/form",
- 		url.Values{"key": {"Value"}, "id": {"123"}})
+		url.Values{"key": {"Value"}, "id": {"123"}})
 
 The client must close the response body when finished with it: