update GetVerificationKey type to match node-jwks-rsa

[kylerm42]

Description

A PR was recently merged to auth0/node-jwks-rsa that changed the type of GetVerificationKey, which breaks the interaction with express-jwt. This PR updates the type here to match the change there.

References

• [Issue that led to node-jwks-rsa change](expressJwtSecret can return undefined which is not reflected in GetVerificationKey type node-jwks-rsa#328
• PR of the actual change
• Fixes GetVerificationKey type doesn't match auth0/node-jwks-rsa #304

Testing

None, does this need a test?

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch

[manast]

Whats holding this PR to be merged?

[jfromaniello]

Thank you, published in v8.1.0.

Note v8 is a major because of a major upgrade in jsonwebtoken, but it should not affect applications on most cases.

[jfromaniello]

And sorry about the delay 🙏