veyron/veyron2/vdl: Stop requiring es6-shim
veyron/veyron2/vdl: Stop requiring es6-shim

vom.js will require it for us when needed, so we can now stop breaking
the build.

Change-Id: If3082f430f35f768dca54a46af2aa4b18da13f6b

vanadium/go.v23,vanadium/go.v23,vanadium/go.v23