Missing @since tag

(introduced into libreoffice-6-0 with cherry-pick
c7fa2da1 "Restore GPG SEInitializer service")

Change-Id: I3ba63f91b3d45591a2cb4804a1792e630093425f

offapi/com/sun/star/xml/crypto/GPGSEInitializer.idl

@@ -26,6 +26,8 @@ module com { module sun { module star { module xml { module crypto {
 
 /**
  * Service of GPGSEInitializer
+ *
+ * @since LibreOffice 6.0
  */
 service GPGSEInitializer : XSEInitializer;