Revert "Add explicit acorn dependency, see https://github.com/phetsims/chipper/issues/1171"
Revert "Add explicit acorn dependency, see https://github.com/phetsims/chipper/issues/1171"

This reverts commit ed383b4e96313e0ba73b44f61ff311f1d9203f66.

phetsims/chipper,phetsims/chipper,phetsims/chipper