Updated Droplet image_id for CentOS

[SethFranklin]

Hi Jeff,

This PR changes the Droplet image_id value from the CentOS 7 id centos-7-x64 to the CentOS stream 9 id centos-stream-9-x64. This is because the older id/slug for CentOS 7 doesn't work on DigitalOcean anymore, and gives me the error below.

PLAY [localhost] ***************************************************************

TASK [Create new Droplet.] *****************************************************
fatal: [localhost]: FAILED! => {"changed": false, "msg": "Failed to create Droplet [HTTP 422: You specified an invalid image for Droplet creation.]"}

PLAY RECAP *********************************************************************
localhost                  : ok=0    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0   

I found a neat web tool that lists all of the valid DigitalOcean API slugs: DigitalOcean API Slugs

Thanks,
Seth

[geerlingguy]

Thanks! I will try to take a look at this and re-test again soon.