Replace the hardcoded copy of Guice multibindings with the Guice extension dependency

A hardcoded copy of Guice multibindings was added to jclouds-chef [1] when they were moved out of Guice core. That package should now be removed and the Guice multibindings extension should be added instead.

[1] https://git-wip-us.apache.org/repos/asf?p=incubator-jclouds-chef.git;a=blob;f=core/src/main/java/org/jclouds/ohai/config/multibindings/package-info.java;h=cccfea44254bd63a68daec1cd8c615e02754ea1d;hb=21fcbcd30040c47114939d95bde8cd8365d234d2