Test reverting to 22.04 for tests

.github/workflows/python-package.yml

@@ -1,7 +1,7 @@
 # -----------------------------------------------------------------------------
 # BSD 3-Clause License
 #
-# Copyright (c) 2020-2024, Science and Technology Facilities Council.
+# Copyright (c) 2020-2025, Science and Technology Facilities Council.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -36,6 +36,7 @@
 # Modified by A. J. Voysey, Met Office
 # Modified by J. Henrichs, Bureau of Meteorology
 # Modified by N. Nobre, STFC Daresbury Lab
+# Modified by A. B. G. Chalk, STFC Daresbury Lab
 
 # This workflow will install Python dependencies, run tests and lint with a
 # variety of Python versions.
@@ -103,7 +104,7 @@ jobs:
     - run: cd doc/developer_guide; make html; make doctest
   build:
     if: ${{ github.repository != 'stfc/PSyclone-mirror' }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
         python-version: [3.7, 3.8, 3.13]