tests: Skip test_readme_examples if README.md is not present #1464

Job	Run time
OS (docker.io/debian:unstable)	1m 55s
OS (docker.io/ubuntu:rolling)	2m 12s
OS (registry.fedoraproject.org/fedora:latest)	2m 39s
OS (docker.io/ubuntu:devel)	2m 4s
OS (registry.fedoraproject.org/fedora:rawhide)	1m 35s
OS (quay.io/centos/centos:stream10-development)	1m 31s
OS (docker.io/ubuntu:latest)	1m 53s
	13m 49s

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