Update gnomad.yaml

[pfpjs]

Fix hg19 and GRCh37 gnomAD recipe

[pfpjs]

While upgrading to the latest version of bcbio-nextgen, it errors out due to $vcf_prefix having been replaced. This fixes it.

/path/to/bcbio/genomes/Hsapiens/hg19/txtmp/ggd-run.sh: line 16: vcf_prefix: unbound variable
Traceback (most recent call last):
  File "/usr/local/bin/bcbio_nextgen.py", line 228, in <module>
    install.upgrade_bcbio(kwargs["args"])
  File "/path/to/bcbio/anaconda/lib/python3.6/site-packages/bcbio/install.py", line 107, in upgrade_bcbio
    upgrade_bcbio_data(args, REMOTES)
  File "/path/to/bcbio/anaconda/lib/python3.6/site-packages/bcbio/install.py", line 359, in upgrade_bcbio_data
    args.cores, ["ggd", "s3", "raw"])
  File “/tmp/tmpbcbio-install/cloudbiolinux/cloudbio/biodata/genomes.py", line 354, in install_data_local
    _prep_genomes(env, genomes, genome_indexes, ready_approaches, data_filedir)
  File “/tmp/tmpbcbio-install/cloudbiolinux/cloudbio/biodata/genomes.py", line 480, in _prep_genomes
    retrieve_fn(env, manager, gid, idx)
  File “/tmp/tmpbcbio-install/cloudbiolinux/cloudbio/biodata/genomes.py", line 875, in _install_with_ggd
    ggd.install_recipe(os.getcwd(), env.system_install, recipe_file, gid)
  File “/tmp/tmpbcbio-install/cloudbiolinux/cloudbio/biodata/ggd.py", line 30, in install_recipe
    recipe["recipe"]["full"]["recipe_type"], system_install)
  File “/tmp/tmpbcbio-install/cloudbiolinux/cloudbio/biodata/ggd.py", line 62, in _run_recipe
    subprocess.check_output(["bash", run_file])
  File "/path/to/bcbio/anaconda/lib/python3.6/subprocess.py", line 336, in check_output
    **kwargs).stdout
  File "/path/to/bcbio/anaconda/lib/python3.6/subprocess.py", line 418, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['bash', '/path/to/bcbio/genomes/Hsapiens/hg19/txtmp/ggd-run.sh']' returned non-zero exit status 1.

[roryk]

Oops. Thank you so much for finding and fixing these!