surface gnomad filter threshold to somatic and immuno workflows

[malachig]

This is related to
#112

[evelyn-schmidt]

My test succeeded. We set the gnomad threshold to 1.1 so that there is no filtering on gnomad data resulting in the final number of variants called to increase from 126 to 149. This is as expected.

[malachig]

To be clear, we do NOT recommend turning off this filter by setting the value > 1. We want the ability to do this in certain edge cases and for experimentation but recommend the current status quo for now (i.e. filtering out variants that appear in gnomad at >0.1% global AF).