deprecate OC_Search_Provider in favor of \OCP\Search\Provider

lib/private/legacy/search/provider.php

@@ -17,6 +17,10 @@
  *
  */
 
+/**
+ * Class OC_Search_Provider
+ * @deprecated use \OCP\Search\Provider instead
+ */
 abstract class OC_Search_Provider extends \OCP\Search\Provider {
 
 }