docs: Update dependencies for latest Envoy
docs: Update dependencies for latest Envoy

After a recent Envoy version bump, Bazel started complaining about:

    libtoolize: not found

Also,

    aclocal: not found

This was because two new build-time dependencies were added. Document
them.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@covalent.io>

michi-covalent/cilium,scanf/cilium,eloycoto/cilium,eloycoto/cilium,scanf/cilium,scanf/cilium,tgraf/cilium,michi-covalent/cilium,scanf/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium,scanf/cilium,tgraf/cilium,scanf/cilium,eloycoto/cilium,michi-covalent/cilium,tklauser/cilium,tklauser/cilium,eloycoto/cilium,cilium/cilium,eloycoto/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,cilium-team/cilium,tgraf/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,eloycoto/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium,scanf/cilium,eloycoto/cilium