no longer override fsaverage with fsaverage6
no longer override fsaverage with fsaverage6

oesteban/fmriprep,oesteban/preprocessing-workflow,poldracklab/fmriprep,poldracklab/fmriprep,poldracklab/fmriprep,oesteban/preprocessing-workflow,oesteban/fmriprep,poldracklab/preprocessing-workflow,poldracklab/preprocessing-workflow,oesteban/fmriprep