You should be able to remove references to ExampleDS without impacting any functionality in the server. ExampleDS was meant to be just that - an example that can be quickly looked within the shipped configurations (without the need to go look into a possibly out of date doc).
Later in the release cycle of WildFly and Java EE7 spec, the concept of "default datasource" was introduced (see EE.5.19 section of Java EE7 spec for more details). The default datasource is expected to be bound into the Java EE component specific namespace (a.k.a ENC) and is available at java:comp/DefaultDataSource. That ENC JNDI name is just a link to the container specific default shipped datasource and in this case just links to java:jboss/datasources/ExampleDS.
So if you do remove that ExampleDS, all you have to do is come up with your own datasource which can be considered as the default datasource and the JNDI name of that datasource is what you use in the <default-bindings> element of the EE subsystem configuration.