fix: remove custom newrelic snippet in favor of new frontend-build one (#832)

webpack.prod.config.js

@@ -1,18 +0,0 @@
-const { getBaseConfig } = require('@edx/frontend-build');
-
-const config = getBaseConfig('webpack-prod');
-
-// Filter plugins in the preset config that we don't want
-function filterPlugins(plugins) {
-  const pluginsToRemove = [
-    'a', // "a" is the constructor name of HtmlWebpackNewRelicPlugin
-  ];
-  return plugins.filter(plugin => {
-    const pluginName = plugin.constructor && plugin.constructor.name;
-    return !pluginsToRemove.includes(pluginName);
-  });
-}
-
-config.plugins = filterPlugins(config.plugins);
-
-module.exports = config;