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!
Is it okay to hardcode `'Administrators'` as the role name?  Shouldn't that look at `AdministratorRoleId` on the Portal?