oauth2/google: fixed comment formatting and clarified naming

google/internal/externalaccount/clientauth.go

@@ -9,7 +9,7 @@ import (
 
 // ClientAuthentication represents an OAuth client ID and secret and the mechanism for passing these credentials as stated in rfc6749#2.3.1.
 type ClientAuthentication struct {
-	//AuthStyle can be either basic or request-body
+	// AuthStyle can be either basic or request-body
 	AuthStyle    oauth2.AuthStyle
 	ClientID     string
 	ClientSecret string
@@ -34,6 +34,4 @@ func (c *ClientAuthentication) InjectAuthentication(values url.Values, headers h
 		values.Set("client_id", c.ClientID)
 		values.Set("client_secret", c.ClientSecret)
 	}
-
-	return
 }