oauth2: context instead of golang.org/x/net/context in doc

Change-Id: I377136feb07354904b2f27600f3aef0629ca76f2
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/632295
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: alexandear

internal/transport.go

@@ -9,8 +9,8 @@ import (
 	"net/http"
 )
 
-// HTTPClient is the context key to use with golang.org/x/net/context's
-// WithValue function to associate an *http.Client value with a context.
+// HTTPClient is the context key to use with [context.WithValue]'s
+// function to associate an *http.Client value with a context.
 var HTTPClient ContextKey
 
 // ContextKey is just an empty struct. It exists so HTTPClient can be

oauth2.go

@@ -22,7 +22,7 @@ import (
 )
 
 // NoContext is the default context you should supply if not using
-// your own context.Context (see https://golang.org/x/net/context).
+// your own [context.Context].
 //
 // Deprecated: Use context.Background() or context.TODO() instead.
 var NoContext = context.TODO()
@@ -338,8 +338,8 @@ func (s staticTokenSource) Token() (*Token, error) {
 	return s.t, nil
 }
 
-// HTTPClient is the context key to use with golang.org/x/net/context's
-// WithValue function to associate an *http.Client value with a context.
+// HTTPClient is the context key to use with [context.WithValue]'s
+// function to associate an *http.Client value with a context.
 var HTTPClient internal.ContextKey
 
 // NewClient creates an *http.Client from a Context and TokenSource.