fix: re-enable flow type checking for the project (#1197)

Flow wasn't working anymore. This fixes flow type checking and it to the git precommit hook.

webpack.renderer.additions.js

@@ -1,6 +1,4 @@
 const path = require('path');
-const FlowFlowPlugin = require('./flowtype-plugin');
-const isDev = require('electron-is-dev');
 
 const ELECTRON_RENDERER_PROCESS_ROOT = path.resolve(__dirname, 'src/renderer/');
 
@@ -23,11 +21,3 @@ module.exports = {
     extensions: ['.js', '.jsx', '.scss'],
   },
 };
-
-if (isDev) {
-  module.exports.plugins = [
-    new FlowFlowPlugin({
-      warn: true,
-    }),
-  ];
-}