chore: fix file permissions and trailing whitespace

- Reset executable bit (100755 → 100644) on three source files
  that were incorrectly marked during cross-filesystem copy
- Remove trailing whitespace on final line of zip-export-dialog.tsx

Author: stephanbuettig

src/components/view/multi-selection-summary-pane.tsx

@@ -862,4 +862,3 @@ export class ZipExportDialog extends React.Component<ZipExportDialogProps> {
         </Overlay>;
     }
 }
-