tasks-rs: Add to README an instruction to comment an import line

The issue is in EnableJsonSupport Manu framework unit. The description below is no more relevant.

Currently maven checkstyle plugin fails on unused import after adding JSON support to the tasks-rs quickstart

tasks-rs/src/main/java/org/jboss/as/quickstarts/tasksrs/service/TaskResource.java:30:8: Unused import - javax.ws.rs.Produces. [UnusedImports]

Our QE tests are fixed now, but for the customers it would be useful to have an instruction to comment the line

import javax.ws.rs.Produces

It would be nice to have this instruction in Modify this Quickstart to Support JSON Representations of Tasks section, step 3, Add comments to this line sentence.

Thanks!