devel/py-pyyaml5: Remove obsoleted port

Use devel/py-pyyaml instead.

This port was added for devel/oci-cli which requires pyyaml < 6. The restriction was relaxed later.

Reference: https://cgit.freebsd.org/ports/commit/?id=af75775bb587e2e801b8aea4fbf62d02fee27d8e