[Glitch] Fix column header scrolling with the page

Port 706a48ee1f to glitch-soc

Signed-off-by: Thibaut Girka <thib@sitedethib.com>

app/javascript/flavours/glitch/features/ui/components/column_loading.js

@@ -21,7 +21,7 @@ export default class ColumnLoading extends ImmutablePureComponent {
     let { title, icon } = this.props;
     return (
       <Column>
-        <ColumnHeader icon={icon} title={title} multiColumn={false} focusable={false} />
+        <ColumnHeader icon={icon} title={title} multiColumn={false} focusable={false} placeholder />
         <div className='scrollable' />
       </Column>
     );