Adjust block inserter style. (#3075)

assets/src/stories-editor/components/inserter/edit.css

@@ -0,0 +1,3 @@
+.amp__block-editor-inserter__menu.block-editor-inserter__menu {
+	flex-direction: column;
+}

assets/src/stories-editor/components/inserter/index.js

@@ -25,6 +25,7 @@ import { withSelect } from '@wordpress/data';
  * Internal dependencies
  */
 import InserterMenu from './menu'; // eslint-disable-line import/no-named-as-default
+import './edit.css';
 
 const defaultRenderToggle = ( { onToggle, disabled, isOpen } ) => (
 	<IconButton

assets/src/stories-editor/components/inserter/menu.js

@@ -274,7 +274,7 @@ export class InserterMenu extends Component {
 		/* eslint-disable jsx-a11y/no-autofocus, jsx-a11y/no-static-element-interactions */
 		return (
 			<div
-				className="editor-inserter__menu block-editor-inserter__menu"
+				className="editor-inserter__menu block-editor-inserter__menu amp__block-editor-inserter__menu"
 				onKeyPress={ stopKeyPropagation }
 				onKeyDown={ this.onKeyDown }
 			>
@@ -285,13 +285,13 @@ export class InserterMenu extends Component {
 					id={ `block-editor-inserter__search-${ instanceId }` }
 					type="search"
 					placeholder={ __( 'Search for an element', 'amp' ) }
-					className="editor-inserter__search block-editor-inserter__search"
+					className="editor-inserter__search block-editor-inserter__search amp__block-editor-inserter__search"
 					autoFocus
 					onChange={ this.onChangeSearchInput }
 				/>
 
 				<div
-					className="editor-inserter__results block-editor-inserter__results"
+					className="editor-inserter__results amp__block-editor-inserter__results block-editor-inserter__results"
 					ref={ this.inserterResults }
 					tabIndex="0"
 					role="region"