Revert "Update SnakeYAML-Engine to 3.0.1"

This reverts commit 599f89d.

Author: headius

lib/psych/versions.rb

@@ -5,6 +5,6 @@ module Psych
   VERSION = '5.3.1'
 
   if RUBY_ENGINE == 'jruby'
-    DEFAULT_SNAKEYAML_VERSION = '3.0.1'.freeze
+    DEFAULT_SNAKEYAML_VERSION = '2.10'.freeze
   end
 end