Need to upgrade the supported the Ansible version

[bxu1999]

With the current setup in README, the following will show:

$ ansible-galaxy collection install operator_sdk.util
Starting galaxy collection install process
[WARNING]: Collection vyos.vyos does not support Ansible version 2.15.4
[WARNING]: Collection ansible.posix does not support Ansible version 2.15.4
[WARNING]: Collection ansible.netcommon does not support Ansible version 2.15.4
[WARNING]: Collection openvswitch.openvswitch does not support Ansible version 2.15.4
[WARNING]: Collection cisco.iosxr does not support Ansible version 2.15.4
[WARNING]: Collection frr.frr does not support Ansible version 2.15.4
[WARNING]: Collection cisco.asa does not support Ansible version 2.15.4
[WARNING]: Collection splunk.es does not support Ansible version 2.15.4
[WARNING]: Collection cisco.ios does not support Ansible version 2.15.4
[WARNING]: Collection cisco.nxos does not support Ansible version 2.15.4
[WARNING]: Collection junipernetworks.junos does not support Ansible version 2.15.4
[WARNING]: Collection ibm.qradar does not support Ansible version 2.15.4
[WARNING]: Collection arista.eos does not support Ansible version 2.15.4
Process install dependency map
Starting collection install process
Downloading https://galaxy.ansible.com/api/v3/plugin/ansible/content/published/collections/artifacts/operator_sdk-util-0.5.0.tar.gz to /home/bxu/.ansible/tmp/ansible-local-4311612vmjaija/tmptmsdnjwq/operator_sdk-util-0.5.0-t5mjinrp
Installing 'operator_sdk.util:0.5.0' to '/home/bxu/.ansible/collections/ansible_collections/operator_sdk/util'
operator_sdk.util:0.5.0 was installed successfully

It's likely that the Ansible version needs to be upgrade to avoid those warnings.