CI: bump ubuntu-20.04 to 22.04 in CI jobs (#475)

Author: rgommers

.github/workflows/ci.yml

@@ -12,15 +12,15 @@ jobs:
         os:
           [
             ubuntu-latest,
-            ubuntu-20.04,
+            ubuntu-22.04,
             macos-13,
             windows-latest,
             windows-2019,
           ]
         exclude:
           - os: ubuntu-latest
             architecture: x86
-          - os: ubuntu-20.04
+          - os: ubuntu-22.04
             architecture: x86
           - os: macos-13
             architecture: x86