Actually save ctx after group sync

Author: Trolldemorted

Signal-Windows.Lib/Storage/DB.cs

@@ -1120,6 +1120,7 @@ internal static List<SignalConversation> InsertOrUpdateGroups(IList<(SignalGroup
                             });
                         }
                     }
+                    ctx.SaveChanges();
                 }
             }
             return refreshedGroups;