Remove typeof 'string' check for secret

[jeffijoe]

A secret can also be a buffer (when passed to jsonwebtoken) and the string check will prevent that.

Offending line: https://github.com/feathersjs/feathers-authentication-jwt/blob/master/src/index.js#L43

[daffl]

Did you try if it works removing this line of code from the code for this package in node_modules?

[jeffijoe]

Yes, it works with that line removed.