x530#delete recursive .certs/pki/default-selfsigned
Delete flash:/.certs/pki/default-selfsigned and all its contents? (y/n)[n]:y Deleting...
If you are not willing to reboot, it is possible to create a new trustpoint, and configure http to use it:
x530(config)#crypto pki trustpoint workaround Created trustpoint "workaround".
x530#crypto pki authenticate workaround Generating 2048-bit key for local CA...
Successfully authenticated trustpoint "workaround".
x530#crypto pki enroll workaround
Generating 2048-bit key "server-default"...
Successfully enrolled the local server.
Enter configuration commands, one per line. End with CNTL/Z.
x530(config)#http trustpoint workaround