Fix javadoc for AgentClient#register (#380)

The QueryOptions agument is NOT optional.
If a null value is passed, a NPE is thrown.

src/main/java/org/kiwiproject/consul/AgentClient.java

@@ -221,7 +221,7 @@ public void register(int port, List<Registration.RegCheck> checks, String name,
      * the use of checks.
      *
      * @param registration          The registration payload.
-     * @param options               An optional QueryOptions instance.
+     * @param options               A QueryOptions instance.
      * @param queryParameterOptions The Query Parameter Options to use.
      */
     public void register(Registration registration, QueryOptions options, QueryParameterOptions queryParameterOptions) {