Document when the vault pki role required setting require_cn=false

[wallrj]

I fixed this by setting require_cn=false in my vault pki role [also i recently updated to vault v1.10.0]:

vault write pki_int/roles/dc \
    allowed_domains=dc \
    allow_subdomains=true \
    require_cn=false \
    max_ttl=72h

Originally posted by @Nold360 in cert-manager/cert-manager#4965 (comment)

[abvijaykumar]

Hi I am getting the following error

"Vault failed to sign certificate: failed to sign certificate by vault: Error making API request. URL: POST http://vault.default:8200/v1/pki/sign/mysite-dot-com Code: 400. Errors: * subject alternate name mysite.com not allowed by this role"