RPM: Fix py3 dependency

[MartinBasti]

Signed-off-by: Martin Basti mbasti@redhat.com

Maintainers will complete the following section

• [ ] Commit messages are descriptive enough
• [ ] Code coverage from testing does not decrease and new code is covered
• [ ] JSON/YAML configuration changes are updated in the relevant schema
• [ ] Pull request has a link to an osbs-docs PR for user documentation updates

[MartinBasti]

Release notes:

Specfile: fixed py3 dependency