website: Update the gem5 versioning to v22.0

Change-Id: I06329f25433be10153ea53f853103a5e0f384aae
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/60514
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
4 files changed