Fix Java example in multitenanci.adoc

[caio-henrique]

• Corrected the Java example of the jwtProcessor function. The function parameter was changed to JWTClaimsSetAwareJWSKeySelector, as described in the section Parsing the Claim Only Once.
• Fixed the Java example of the jwtDecoder function. The name of the variable used in the NimbusJwtDecoder constructor has been changed to jwtProcessor.