Update downloads page to include new v4.1 files

[ch-kr]

Update v4 downloads to reflect updated files for the v4.1 release:

• Short variants: updated Hail Tables and VCFs for exomes, genomes, new joint table
  • Add new sections/links for new joint exomes/genomes frequency data (Hail Table) new all sites allele number (AN) Hail Table and TSVs
• Constraint: updated constraint Hail Table, TSV, and README
• SV: updated per-chromosome SV VCFs (see Xuefang's post)
• CNV: updated CNV VCFs (all gnomad exomes + two subsets)
• New and if ready for v4.1: include section for v2.1.1 liftover VCF and HT filtered to three clinically relevant genes; see paper and prod ticket for more details
• Add link to new REVEL downloadable TSVs (contain max REVEL scores for missenses in ~2k genes that were previously missing scores) (related to https://github.com/broadinstitute/gnomad-browser/issues/1447). There will be three total files: two TSVs (one for exomes, one for genomes) and a README file

Sheet where we will be tracking files to sync

[ch-kr]

Proposed links for these files:

Add new sections/links for new joint exomes/genomes frequency data (Hail Table) new all sites allele number (AN) Hail Table and TSVs

• https://gnomad.broadinstitute.org/downloads#v4-all-sites-allele-number
• https://gnomad.broadinstitute.org/downloads#v4-joint-freq-stats

(cc @mike-w-wilson @jkgoodrich in case they have suggestions for naming)