Change python3.4 to python3
### Existing feature/capability to improve
Job to build docs needs to be updated to use `python3` instead of `python3.4` to match recent changes upstream.
### Testing requirements
None
### Define success
Pipeline passes again
### Environment info
- OpenCPI Version: develop
- Type of install (RPM or source): Source
- Operating System and version (`uname -a`):
- Link to your project on GitLab (optional):
### Links/references
opencpi/opencpi!169
issue