As described in https://github.com/ansible/ansible/issues/65687, get_url
only partially supports check_mode: "the changed status will reflect
comparison to an empty source file".
Before this change, executing this code, with the key already being in
place on the target system, would report "OK", while check_mode would
report "changed".
Due to this change, both now either report "OK" or "changed", depending
on the state of the target system.
