fix: remove generating .eslintcache

fixes facebook#10161

No need to generate eslint cache due to performance boost
gained in eslint-webpack-plugin 2.4.1

Author: falinsky

packages/react-scripts/config/webpack.config.js

@@ -756,7 +756,6 @@ module.exports = function (webpackEnv) {
         formatter: require.resolve('react-dev-utils/eslintFormatter'),
         eslintPath: require.resolve('eslint'),
         context: paths.appSrc,
-        cache: true,
         // ESLint class options
         cwd: paths.appPath,
         resolvePluginsRelativeTo: __dirname,