refactor: remove id lookup model overwrite at EG
refactor: remove id lookup model overwrite at EG

By looking closely the differences between this version at EG and the version
at ensembl-rest, I believe we can safely remove this module from eg-rest. This
will make things simpler for the future.

Related to ENSEMBL-4859.

EnsemblGenomes/eg-rest,EnsemblGenomes/eg-rest