fix: T2w image of MNI template unavailable in Singularity
fix: T2w image of MNI template unavailable in Singularity

Prefetch this image so that MRIQC works more smoothly with Singularity

Closes: #918.

oesteban/mriqc,oesteban/mriqc,oesteban/mriqc,oesteban/mriqc