resources: Update version info to v21.2

Change-Id: I60a32e310bb6e42435fd056a0e33e62e98eaa38e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/54723
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby Bruce <bbruce@ucdavis.edu>
5 files changed