Fix icons

Summary:
`cross-outline` doesn't seem to be a thing anymore.

https://external.xx.fbcdn.net/assets/?name=cross-outline&variant=filled&size=16&set=facebook_icons&density=1x

Reviewed By: danielbuechele

Differential Revision: D15822731

fbshipit-source-id: d0becbd9faa60393a4be1ef9f4d6bf8da7e9bc20

src/plugins/fresco/ImagesCacheOverview.js

@@ -162,7 +162,7 @@ export default class ImagesCacheOverview extends PureComponent<
         onKeyDown={this.onKeyDown}
         tabIndex="0">
         <Toolbar position="top">
-          <Button icon="cross-outline" onClick={this.props.onTrimMemory}>
+          <Button icon="trash" onClick={this.props.onTrimMemory}>
             Trim Memory
           </Button>
           <Button onClick={this.props.onRefresh}>Refresh</Button>