website: Add v20.1.0.5 Doxygen link

Change-Id: I512af83665ab483487e0bbeb5791dcc953674e85
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/43385
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
1 file changed