Don't provide favorite activity settings

Since mails and notifications are only available for actions of other users
it does not make sense to allow changing this.
It also prevents the common misunderstanding with
"file was changed inside a favorited folder"

Signed-off-by: Joas Schilling <coding@schilljs.com>

apps/files/lib/Activity/Settings/FavoriteAction.php

@@ -55,7 +55,7 @@ public function getPriority() {
 	 * @since 11.0.0
 	 */
 	public function canChangeStream() {
-		return true;
+		return false;
 	}
 
 	/**
@@ -71,7 +71,7 @@ public function isDefaultEnabledStream() {
 	 * @since 11.0.0
 	 */
 	public function canChangeMail() {
-		return true;
+		return false;
 	}
 
 	/**
@@ -81,4 +81,12 @@ public function canChangeMail() {
 	public function isDefaultEnabledMail() {
 		return false;
 	}
+
+	/**
+	 * @return bool True when the option can be changed for the notification
+	 * @since 20.0.0
+	 */
+	public function canChangeNotification() {
+		return false;
+	}
 }