Do not scroll in the compose panel on single-column (#11093)

app/javascript/mastodon/features/ui/components/compose_panel.js

@@ -8,7 +8,7 @@ const ComposePanel = () => (
   <div className='compose-panel'>
     <SearchContainer openInRoute />
     <NavigationContainer />
-    <ComposeFormContainer />
+    <ComposeFormContainer singleColumn />
     <LinkFooter withHotkeys />
   </div>
 );