Fixed some accessibility issues in the dialogs:

1) Aria-label additions at few missing places.
  2) Label additions with  'sr-only' class where hidden labels required.
  3) Converted label to span to solve accessibility error.

Fixes #4608

web/pgadmin/tools/restore/static/js/restore_dialog_wrapper.js

@@ -38,6 +38,7 @@ export class RestoreDialogWrapper extends DialogWrapper {
           type: 'button',
           url: 'backup.html',
           label: gettext('Restore'),
+          'aria-label': gettext('Object Help'),
         },
       }, {
         text: '',