Update lint section for molecule v3

Update lint section for molecule v3

Starting with Molecule v3 the linting section has been changed to
straight up shell and no longer supports the old v2 format.

This also removes default Molecule files, which are no longer needed,
and would require unnecessary upkeep.

Ref: https://molecule.readthedocs.io/en/latest/configuration.html#lint
Signed-off-by: Thanh Ha <zxiiro@gmail.com>
Signed-off-by: Eric Ball <eball@linuxfoundation.org>
Change-Id: Iaa40efc377409e08e6efd41aa967249f9d3c4bbd