Figure out what to do with the xwiki-platform-notifications-preferences-default dependency added in Confluence Migrator Pro

[raphj]

Commit d8ecb35e (@trrenty) in Confluence Migrator Pro added the following in application-confluence-migrator-pro-converters/pom.xml:

    <!-- Needed by the task manager dependencies. It can cause problems during testing but possibly in production as
      well. Should probably be added to the task manager instead and have it removed here once it's done. -->
    <dependency>
      <groupId>org.xwiki.platform</groupId>
      <artifactId>xwiki-platform-notifications-preferences-default</artifactId>
      <version>${platform.version}</version>
    </dependency>

This comment should be acted upon so we can remove that dependency from Confluence Migrator Pro.