Revisit revocation related to InvalidityDate

Currently under ocsp spec section 3.i.a:

If the invalidity date is present and the authentic signing time is also present then if the invalidity date is before the authentic signing time, the certificate is considered revoked.

We need to revisit this part:

1. Do we want to keep this part as the invalidity date is not always accurate, it depends on the ca.
2. It we decide to keep it, according to @priteshbandi: refactor!: update revocation notation-core-go#215 (comment), the authentic signing time part is misleading and we need to fix it.