Are you running this on a Spark cluster or something else? If you’re not on a Spark cluster, you probably need to set PYSPARK_SUBMIT_ARGS to permit Hail to use more memory.
I also strongly, strongly recommend you convert your data into a Hail native format before continuing with any serious analysis. You can do that like this:
import hail as hl
hl.import_vcf('c1_b2_v1.vcf.bgz').write('c1_b2_v1.mt')
Then you can load that dataset with:
mt = hl.read_matrix_table('c1_b2_v1.mt')