try on ubuntu 22.04 (#6418)

Author: graingert

.github/workflows/run-tests.yml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
-        os: [ubuntu-18.04, macOS-latest, windows-latest]
+        os: [ubuntu-22.04, macOS-latest, windows-latest]
         include:
           # pypy-3.7 on Mac OS currently fails trying to compile
           # brotlipy. Moving pypy3 to only test linux.