Committed Changes for DNN-5909 - GetFoldersByPermission Performance Improvement

Changes to the GetFoldersbyPermission procedure to improve performance.  Change was removing "Users" and "UserRoles" from the last query in the procedure.  These tables are un-used, not returned, and not filtering any data.  Removing these reduce the CPU cost greatly.  Full details on DNN JIRA ticket 5909!
@BrandonHaynes had a great note in the forums that removing the join includes folder permissions where `RoleID` is `NULL` (i.e. permissions assigned to a single user), whereas before they were being removed through that left join. It seems to me that including those would be the correct thing to do (i.e. the previous behavior was a bug, in addition to a performance problem), but does anyone know for sure if there's a reason those _should_ be filtered out?