CI: Use ubuntu-22.04 to support Python 3.7

Author: amotl

.github/workflows/tests.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: ['ubuntu-latest', 'macos-latest']
+        os: ['ubuntu-22.04', 'macos-latest']
         python-version: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
         cratedb-version: ['5.8.3']