CI: Update Ubuntu runner 20.04 -> 22.04.

Author: kinetiknz

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-20.04, windows-2019, macos-13]
+        os: [ubuntu-22.04, windows-2019, macos-13]
         rust: [stable]
         release: [true, false]
         experimental: [false]