Just read the below error message:
ssh: Could not resolve hostname centosinstance: Name or service not known
Ansible can't be able to resolve the centosinstance hostname.
Modify your inventory like this:
centosinstance ansible_ssh_host=192.168.1.10
centosinstance1 ansible_ssh_host=192.168.1.11
Change the ip addresses with the ip addresses of your machines and try one more time.
Hope that help it will resolve your problem.