net/http: remove accidental heading in Head documentation

This short sentence was missing a period at the end, which caused it
to be interpreted as a heading. It also gained a '# ' prefix as part
of new gofmt formatting applied in CL 384268. This change makes it a
regular sentence as originally intended.

Updates #51082.

Change-Id: I100410cca21e4f91130f1f3432327bb6d66b12a2
Reviewed-on: https://go-review.googlesource.com/c/go/+/418959
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/net/http/client.go

@@ -896,7 +896,7 @@ func (c *Client) PostForm(url string, data url.Values) (resp *Response, err erro
 //	307 (Temporary Redirect)
 //	308 (Permanent Redirect)
 //
-// # Head is a wrapper around DefaultClient.Head
+// Head is a wrapper around DefaultClient.Head.
 //
 // To make a request with a specified context.Context, use NewRequestWithContext
 // and DefaultClient.Do.