Move background colour auto-detect script to where the other webpack files are

app/javascript/mastodon/components/error_boundary.js

@@ -2,7 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import defaultmascotlight from '../../images/defaultmascotlight.svg';
 import defaultmascotdark from '../../images/defaultmascotdark.svg';
-import {svgSelect} from '../features/compose/util/svg_select';
+import {svgSelect} from '../svg_select';
 
 export default class ErrorBoundary extends React.PureComponent {
 

app/javascript/mastodon/features/compose/index.js

@@ -15,7 +15,6 @@ import { changeComposing } from '../../actions/compose';
 import defaultmascotlight from '../../../images/defaultmascotlight.svg';
 import defaultmascotdark from '../../../images/defaultmascotdark.svg';
 import { mascot } from '../../initial_state';
-import {svgSelect} from './util/svg_select';
 import Icon from 'mastodon/components/icon';
 
 const messages = defineMessages({
@@ -38,7 +37,7 @@ let instanceMascot;
 if (mascot) {
   instanceMascot = <img alt='' draggable='false' src={mascot} />;
 } else {
-  instanceMascot = <img alt='' draggable='false' className="defaultmascot" src={svgSelect(defaultmascotlight, defaultmascotdark)} />;
+  instanceMascot = <img alt='' draggable='false' className="defaultmascot" src={defaultmascotdark} />;
 }
 
 export default @connect(mapStateToProps)