You don't delete subscription records because you can't. You have to remove them from sale. This will exclude them from future app submissions and any code in the app that handles subscriptions or purchases must be removed or strip from the build at build time. Removing the subscription records from sale or the store allows a user that hasn't updated to continue to have access to the features until they are able to update to the new build.
Topic:
App Store Distribution & Marketing
SubTopic:
App Review
Tags: