Remove DOCTYPE from DocBook template
Remove DOCTYPE from DocBook template

Hopefully fixes Travis CI build failure due to FOP upgrade.

estan/protoc-gen-doc,dr-joy/protoc-gen-doc,estan/protoc-gen-doc,pseudomuto/protoc-gen-doc,pseudomuto/protoc-gen-doc,dr-joy/protoc-gen-doc,estan/protoc-gen-doc