dependencies: upgrade com.google.common.html.types to a newer version

[Nick Santos]

Could you upgrade com.google.common.html.types to 1.0.6 or greater? Right now, closure-templates is pinned to 1.0.4.

https://github.com/google/closure-templates/blob/master/pom.xml#L163

Version 1.0.4 depends on all of GWT, which is deeply unfortunate, see:
google/safe-html-types#5