settings.yml: Use CentOS provided vagrant boxes

We previously switched[1] from official CentOS vagrant boxes as they
were not regularly updated. But the situation has improved a lot since
the last year where boxes are more frequently updated. On top of all
that vagrant cloud platform(HCP-Hashicorp Cloud Platform) has recently
implemented rate limits for downloading boxes[2]. Given all these facts
it is better to get back to official CentOS vagrant boxes. These are
externally hosted on CentOS cloud(and properly redirected from HCP)
allowing us to bypass the throttling seen with HCP.

[1] d1a8534
[2] hashicorp/vagrant#13590

Signed-off-by: Anoop C S <[email protected]>

Author: anoopcs9

playbooks/settings.yml

@@ -184,7 +184,7 @@ tests:
 provisioners:
   vagrant:
     images:
-      centos9: generic/centos9s
+      centos9: centos/stream9
 
     networks:
       private: 192.168.122.0/24