Replace add_variant with contents.add to eliminate deprecation warnings.
Replace add_variant with contents.add to eliminate deprecation warnings.

denkungsart/solidus_digital,brioux/spree_digital,davekiss/spree_digital,davekiss/spree_digital,denkungsart/solidus_digital,spree-contrib/spree_digital,taniarv/spree_digital,taniarv/spree_digital,spree-contrib/spree_digital,taniarv/spree_digital,denkungsart/solidus_digital,brioux/spree_digital,AnnArborTees/spree_digital,spree-contrib/spree_digital,brioux/spree_digital,AnnArborTees/spree_digital,AnnArborTees/spree_digital