Use pre-exisiting type for SecureRandom

Author: egregius313

java/ql/lib/semmle/code/java/security/WeakRandomnessQuery.qll

@@ -30,9 +30,8 @@ private class RandomMethodSource extends WeakRandomnessSource {
  */
 abstract private class SafeRandomImplementation extends RefType { }
 
-private class TypeSecureRandom extends SafeRandomImplementation {
-  TypeSecureRandom() { this.hasQualifiedName("java.security", "SecureRandom") }
-}
+private class TypeSecureRandom extends SafeRandomImplementation instanceof SecureRandomNumberGenerator
+{ }
 
 private class TypeHadoopOsSecureRandom extends SafeRandomImplementation {
   TypeHadoopOsSecureRandom() {