Upadate the docs/tag.d for certificate_authority tag

[varsharain-a11y]

Update ### Tag - certificate_authority description here:

cp-ansible/docs/TAGS.md

Line 16 in 41620d6

### Tag - certificate_authority

Tag - certificate_authority alongside creating self signed certificates also generates the MDS token key pair : private key and public certificate to be used in the MDS.
ansible/blob/41620d6b313a91b154e3f341b99bf8ff86658002/playbooks/tasks/certificate_authority.yml#L118
"Description: To generate the certificate authority (CA) if TLS encryption is enabled and using self-signed certificates .Additionally, it will generate a key pair for the MDS token: a private key and a public certificate for use in the MDS. "