Uninstall pyvcf

From looking at package-popularity data, I don't see it
be imported: https://grafana.datahub.berkeley.edu/d/1EJ3WNi7z/python-popularity-contest-copy?orgId=1&from=now-30d&to=now&viewPanel=8

It fails to install with setuptools>58 - see
jamescasbon/PyVCF#332.

deployments/datahub/images/default/requirements.txt

@@ -97,7 +97,6 @@ hdbscan==0.8.27
 
 # espm 125/bio 105; fall 2019
 # see https://github.com/berkeley-dsep-infra/datahub/issues/1796
-pyvcf==0.6.8
 bitarray==2.3.0
 nlmpy==1.0.1