http: doc nits

Remove the last two "convenience" mentions.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5344041

src/pkg/net/http/client.go

@@ -143,7 +143,7 @@ func shouldRedirect(statusCode int) bool {
 //
 // Caller should close r.Body when done reading from it.
 //
-// Get is a convenience wrapper around DefaultClient.Get.
+// Get is a wrapper around DefaultClient.Get.
 func Get(url string) (r *Response, err error) {
 	return DefaultClient.Get(url)
 }

src/pkg/net/http/header.go

@@ -30,8 +30,8 @@ func (h Header) Set(key, value string) {
 
 // Get gets the first value associated with the given key.
 // If there are no values associated with the key, Get returns "".
-// Get is a convenience method.  For more complex queries,
-// access the map directly.
+// To access multiple values of a key, access the map directly
+// with CanonicalHeaderKey.
 func (h Header) Get(key string) string {
 	return textproto.MIMEHeader(h).Get(key)
 }