verified with 4.5.0-0.nightly-2020-09-12-040057 and issue has been fixed. the default ingresscontroller can be deleted and no error "failed to delete dnsrecord" in the logs
*** Bug 1876919 has been marked as a duplicate of this bug. ***
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (OpenShift Container Platform 4.5.11 bug fix update), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:3719