Bump Ubuntu to 22.04 (#36)

Co-authored-by: repo-helper[bot] <74742576+repo-helper[bot]@users.noreply.github.com>

Author: repo-helper[bot]

.github/workflows/mypy.yml

@@ -20,7 +20,7 @@ jobs:
 
     strategy:
       matrix:
-        os: ['ubuntu-20.04', 'windows-2019']
+        os: ['ubuntu-22.04', 'windows-2019']
       fail-fast: false
 
     steps:

.github/workflows/python_ci_linux.yml

@@ -19,8 +19,8 @@ permissions:
 
 jobs:
   tests:
-    name: "ubuntu-20.04 / Python ${{ matrix.config.python-version }}"
-    runs-on: "ubuntu-20.04"
+    name: "ubuntu-22.04 / Python ${{ matrix.config.python-version }}"
+    runs-on: "ubuntu-22.04"
     continue-on-error: ${{ matrix.config.experimental }}
     env:
       USING_COVERAGE: '3.8'