cert_expiry in Fidelity not used anywhere

[rishkwal]

Currently we have cert_expiry in our Fidelity Bond structure. This cert_expiry is also a part of the fidelity certificate. They can be used in conjugation with network certificate but don't serve any purpose in our current implementation.

[mojoX911]

In tor we don't have network certificates. I also don't see a lot of use of the cert expiry. I vote for removing it. @Wukong247 might have other ideas.