Revert "Install older bundler version in kitchen test"

This reverts commit d1d2eb0f1cedb402daddf6bfff79379fc8760dd5.

Change-Id: Ibfc0b847bf4f355040df8d6b9540440309f5513a
diff --git a/src/com/mirantis/mk/Ruby.groovy b/src/com/mirantis/mk/Ruby.groovy
index f9df3ad..3c96b29 100644
--- a/src/com/mirantis/mk/Ruby.groovy
+++ b/src/com/mirantis/mk/Ruby.groovy
@@ -21,7 +21,7 @@
  * Install kitchen tools
  */
 def installKitchen(kitchenInit=""){
-    sh """rbenv exec gem install bundler -v '~> 1.15.4' --conservative;
+    sh """rbenv exec gem install bundler --conservative;
           rbenv exec gem install test-kitchen --conservative;"""
     if(kitchenInit!=""){
         sh kitchenInit