Disable End users creating Distribution List using OWA

That's a "permission" setting which you can remove. Go to the O365 admin portal -> Exchange -> Permissions -> User roles -> double-click the default policy -> remove the checkbox next to MyDistributionGroups.

If you want to do this only for a subset of users, create a new policy and apply it as needed.

If you want to still allow them to manage groups they own, but stop them from creating new ones, you have to do it like this: https://blogs.technet.microsoft.com/rmilne/2013/08/09/allow-users-to-manage-distribution-groups-without-creating-new-ones/