This disablePolicyChecks configuration cannot be found, and istio does not provide best practices for rate limiting.
disable_policy_checks should still be an option (though deprecated): https://github.com/istio/api/blob/0dc35ad5c478f531f3453749395fcd94e40eb405/mesh/v1alpha1/config.proto#L58.
There is a guide to maintaining Mixer-integrated policy checks, if still needed here.
If I may ask, what are your rate limiting needs?
cc: @gargnupur for visibility