Fix the documentation about the ejb layer to mention it pulls the ejb-local-cache one by default

This is a follow up to https://issues.redhat.com/browse/WFWIP-458, see https://issues.redhat.com/browse/WFWIP-458?focusedCommentId=20101863&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-20101863.

When the ejb layer is used, the ejb-local-cache is implicitly pulled.
We need to advertise this for the case when the user would like to leverage ejb-dist-cache instead, so that they're aware that ejb-local-cache MUST be excluded explicitly.

See https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.3/html-single/using_eclipse_microprofile_with_jboss_eap_xp_2.0.0/index#decorator-provisioning-layers_default