Release Note: Signature and SignatureSpi Get Parameter Methods May Return null When Unsupported

[Signature.getParameters()](https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/security/Signature.html#getParameters()) and [SignatureSpi.engineGetParameters()](https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/security/SignatureSpi.html#engineGetParameters()) may return null if the underlying provider does not support returning the parameters as AlgorithmParameters. For further details, see the Signature and SignatureSpi method descriptions.