change for show scroll vertical

[alirezamhi]

Thank you for contributing to vis.js!!

Please make sure to check the following requirements before creating a pull request:

• All pull requests must be to the master branch.
• Make sure your changes are based on the latest version of the master branch. (Use e.g. git fetch && git rebase origin master to update your feature branch).
• Provide an additional or update an example to demonstrate your changes or new features.
• Update the documentation if you introduced new behavior or changed existing behavior.
• Reference issue numbers of issues that your pull request addresses. (If you write something like fixes #1781 in your git commit message this issue gets closed automatically by merging your pull request).
• Expect review comments and change requests by reviewer.

[alirezamhi]

I write this problem in this issue