Remove duplicate calls to the cache provider

[jamiees2]

Description

Replay of node-saml/passport-saml#596 onto this repo:

When validateInResponseTo isn't set to true, we end up setting it to false here: https://github.com/node-saml/passport-saml/blob/13c7216644ba055217fc97b41df63301be982137/src/node-saml/saml.ts#L155

This value was then checked if it's not null here, which is always true. The intention was likely to have this check check if the value was true, like everywhere else this value is used. This changes the gate to just check if the value is true.

This is a small enough change so I won't default to writing a test for this edge behavior - an extra delete call to the cache provider isn't a big deal, but I found this when debugging our custom cache provider.

Checklist:

• Issue Addressed: [x]
• Link to SAML spec: [ ]
• Tests included? [ ]
• Documentation updated? [ ]