WordPress.Security.NonceVerification.NoNonceVerification: Remove outdated reference from WordPress-VIP-Go ruleset and let inheritance from parent

[rebeccahum]

Fixes #605.

[GaryJones]

Approved - in this case, NoNonceVerification hasn't existed in WPCS since 2.0.0, and we've required WPCS 2.1.0 as a dev dependency since VIPCS 2.0, so all good.

[jrfnl]

Reviewed after the fact.

Notes:

This commit constitutes a functional change, though in reality that change took effect once WPCS 2.0 was required via Composer.

Previously there was only one error code in WPCS from the NonceVerification sniff - NoNonceVerification -. This same error code would throw a warning or an error depending on whether or not a superglobal was referenced. Both would have severity 5.

The ruleset change in VIP Go effectively, turned all notices from the NonceVerification sniff into warnings with severity 10.

Once WPCS 2.0 was required, the ruleset change in VIP Go no longer had any effect and the sniff would now throw the Missing error and the Recommended warning at severity 5.

This update formalizes the current status-quo by removing the reference from the VIP Go ruleset.
The "old" situation of turning violations from the NonceVerification sniff into warnings with severity 10 is effectively abandoned by this change.