Update policy files in java/drda/org/apache/derby/drda

The java/drda/org/apache/derby/drda/template.policy and java/drda/org/apache/derby/drda/server.policy files both include the following line, which I understand is no longer needed:

permission java.util.PropertyPermission "derby.storage.jvmInstanceId",
"write";

It should be removed from both.

Possibly the template.policy file, which is used as the JDK demos/db/templates/server.policy file, should have some further changes to reflect current recommendations.