Update README installation information

[alisonlhart]

This section https://github.com/redhat-cop/network.ospf#installation in the README needs to be updated with the correct install information.

Since the collection is now on Automation Hub, instead of installing from ansible-galaxy collection install git+https://github.com/redhat-cop/network.ospf, install directly with the collection name: ansible-galaxy collection install network.ospf.

The requirements.yml section should also be updated to show network.ospf instead of the repository link.

Any other install references (if relevant) should be updated in the same way.

If there is no upcoming release planned to Automation Hub, please make a one-off minor release for this fix, so customers can receive the updated docs as soon as possible.