Minor cleanup

packages/grafana-ui/src/themes/dark.js

-
-
 const defaultTheme = require('./default');
 const tinycolor = require('tinycolor2');
 

packages/grafana-ui/src/utils/storybook/themeKnob.ts

-import { select } from '@storybook/addon-knobs';
-import { GrafanaTheme } from '../../types';
-
-export const getThemeKnob = (defaultTheme: GrafanaTheme = GrafanaTheme.Dark) => {
-  return select(
-    'Theme',
-    {
-      Default: defaultTheme,
-      Light: GrafanaTheme.Light,
-      Dark: GrafanaTheme.Dark,
-    },
-    defaultTheme
-  );
-};