Update parser gem to remove warning about wrong ruby version

Gemfile.lock

@@ -573,8 +573,8 @@ GEM
     parallel (1.12.0)
     paranoia (2.3.1)
       activerecord (>= 4.0, < 5.2)
-    parser (2.4.0.0)
-      ast (~> 2.2)
+    parser (2.4.0.2)
+      ast (~> 2.3)
     parslet (1.5.0)
       blankslate (~> 2.0)
     path_expander (1.0.1)