Fix npm run dev (#2030)

Summary:
**Summary**

Fixes the `npm run dev` command, which currently fails when run.

**Test Plan**

`npm run dev`
`yarn run dev`
Pull Request resolved: #2030

Differential Revision: D14406346

fbshipit-source-id: 9a689d4ef3097a2728f5603d20097b98b6c3a8df

Author: fabiomcosta

gulpfile.js

@@ -245,7 +245,9 @@ gulp.task(
 
 gulp.task(
   'website:static',
-  gulp.series('dist:min', 'css',
+  gulp.series(
+    'dist:min',
+    'css',
     gulp.parallel(function() {
       return gulp
         .src(paths.dist + '/Draft.min.js')
@@ -256,7 +258,7 @@ gulp.task(
         .src(paths.dist + '/Draft.css')
         .pipe(gulp.dest(paths.static + '/css'));
     }),
-  )
+  ),
 );
 
 gulp.task(
@@ -269,14 +271,14 @@ gulp.task(
 gulp.task(
   'watch',
   gulp.series(function() {
-    gulp.watch(paths.src, ['modules']);
+    gulp.watch(paths.src, gulp.parallel('modules'));
   }),
 );
 
 gulp.task(
   'dev',
   gulp.series(function() {
-    gulp.watch(paths.src, ['modules', 'dist']);
+    gulp.watch(paths.src, gulp.parallel('dist'));
   }),
 );