ci: Use Ubuntu 22.04 runners

Ubuntu 20.04 is now unsupported.

Link: https://github.com/actions/runner-images/issues/11101

.github/workflows/CICD.yml

@@ -36,7 +36,7 @@ jobs:
 
   ensure_cargo_fmt:
     name: Ensure 'cargo fmt' has been run
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
     - uses: dtolnay/rust-toolchain@stable
       with:
@@ -56,7 +56,7 @@ jobs:
 
   min_version:
     name: Minimum supported rust version
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     needs: crate_metadata
     steps:
     - name: Checkout source code