Removed mpi4py from yank build: section.
Removed mpi4py from yank build: section.


Former-commit-id: 5b75a91ec186838d2923fc981f816404060038cf
mpharrigan/conda-recipes,jchodera/conda-recipes,mpharrigan/conda-recipes,marscher/omnia-conda-recipes,cwehmeyer/conda-recipes,jchodera/conda-recipes,danielparton/omnia-md-conda-recipes,swails/conda-recipes,mpharrigan/conda-recipes,rmcgibbo/conda-recipes,swails/conda-recipes,swails/conda-recipes,marscher/omnia-conda-recipes,cwehmeyer/conda-recipes,omnia-md/conda-recipes,rmcgibbo/conda-recipes,cwehmeyer/conda-recipes,omnia-md/conda-recipes,jchodera/conda-recipes,swails/conda-recipes,danielparton/omnia-md-conda-recipes,omnia-md/conda-recipes,jchodera/conda-recipes,cwehmeyer/conda-recipes,rmcgibbo/conda-recipes,peastman/conda-recipes,rmcgibbo/conda-recipes,marscher/omnia-conda-recipes,peastman/conda-recipes,marscher/omnia-conda-recipes,peastman/conda-recipes