CI: Use Ubuntu 22.04.

Author: kinetiknz

.github/workflows/build.yml

@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     continue-on-error: ${{ matrix.experimental }}
     strategy:
       fail-fast: false