somatic wgs does not include gnomad filtering

[chrisamiller]

we use it in exome, in the filter_vcf step, but the gnomad vcf we're using is only a subset, restricted to exome coords. Would be nice to revisit that decision at some point (options: leave it out, apply it to exome only, or find a new genome-wide VCF)

[malachig]

presumably we can now get a genome-wide VCF from GNOMAD v3 which would seem a good solution here.