Enforce import order with ESLint (#25096)

app/javascript/mastodon/reducers/height_cache.js

@@ -1,4 +1,5 @@
 import { Map as ImmutableMap } from 'immutable';
+
 import { HEIGHT_CACHE_SET, HEIGHT_CACHE_CLEAR } from '../actions/height_cache';
 
 const initialState = ImmutableMap();