chore: Update DigitalOcean provider package

[jkpe]

This PR

• fixes the example file do-provider-install.yaml to use a working package
• updates the README with relevant changes

[jkpe]

@diabhey can you help with getting the dev centre article updated? 👍 ❤️

https://www.digitalocean.com/community/developer-center/setting-up-a-doks-egress-gateway-using-crossplane-and-static-routes-operator

[diabhey]

@jkpe : Developer center tutorials is a PR away. https://github.com/digitalocean/tutorials