8159009: Remove ExemptionMechanism.finalize() implementation

Reviewed-by: mullan, weijun

jdk/src/java.base/share/classes/javax/crypto/ExemptionMechanism.java

@@ -482,13 +482,4 @@ public class ExemptionMechanism {
         done = true;
         return n;
     }
-
-    /**
-     * Ensures that the key stored away by this ExemptionMechanism
-     * object will be wiped out when there are no more references to it.
-     */
-    protected void finalize() {
-        keyStored = null;
-        // Are there anything else we could do?
-    }
 }