Simplify Mix Browsersync API

Since upstream changes were merged which make the default files to watch
use the publicPath (laravel-mix/laravel-mix#2091). One caveat is that
those the default files to watch doesn’t include `config/*.php`, but the
impact for us would be low since those files probably wouldn’t be
changing a ton. It could be something we make another upstream PR for
since it could be beneficial to the Laravel community as well.

webpack.mix.js

@@ -21,13 +21,7 @@ const src = path => `resources/assets/${path}`;
 mix.setPublicPath('./dist');
 
 // Browsersync
-mix.browserSync({
-  proxy: 'https://example.test',
-  files: [
-    '(app|config|resources)/**/*.php',
-    publicPath`(styles|scripts)/**/*.(css|js)`,
-  ],
-});
+mix.browserSync('example.test');
 
 // Styles
 mix.sass(src`styles/app.scss`, 'styles');