util-docker: Update systemc docker image to use 22.04

Updates the Dockerfile, and therefore the Docker image, to use Ubuntu
22.04 instead of Ubuntu 20.04.

Change-Id: I0969205159d47ece9b0b6c0452ce0f3420f32e4c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/69317
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
1 file changed