Docs: Security JWT guide minor fixes

[michalvavrik]

I read and tested https://quarkus.io/version/main/guides/security-jwt and propose very minor changes:

• there is a space between java.security. and Principal
• JSR 250 annotations are now Jakarta Annotations
• 401 response body is empty, thus dropping Not authorized
• publicKey.pem needs to be treated in uniform fashion and later it is enclosed with code quotes
• SecurityResource adding missing imports, dropping unused import and variable, adding throws clause, making secret constant (which it de-facto was)

https://quarkus.io/version/main/guides/security-jwt-build

• smallrye.jwt.sign.key.location has sign() and innerSign() as code, while smallrye.jwt.sign.key has them as a plain text (and their are right next to each other) so I'd like it to be same

[github-actions]

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[sberyozkin]

Thanks for this clean up Michal