ci(runners): upgrade CI runners to Ubuntu 22.04 (#138)

Updates CI runners to use Ubuntu 22.04 in the `maint-0.9` branches
because 20.04 is not supported anymore. Also removes Python 3.6 from the
test matrix because the runners do not support it anymore.

Author: tiborsimko

.github/workflows/ci.yml

@@ -1,5 +1,5 @@
 # This file is part of REANA.
-# Copyright (C) 2020, 2021, 2022, 2023, 2024 CERN.
+# Copyright (C) 2020, 2021, 2022, 2023, 2024, 2025 CERN.
 #
 # REANA is free software; you can redistribute it and/or modify it
 # under the terms of the MIT License; see LICENSE file for more details.
@@ -10,7 +10,7 @@ on: [push, pull_request]
 
 jobs:
   lint-commitlint:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -36,7 +36,7 @@ jobs:
           ./run-tests.sh --check-commitlint ${{ github.event.pull_request.head.sha }}~${{ github.event.pull_request.commits }} ${{ github.event.pull_request.head.sha }}
 
   lint-shellcheck:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -47,15 +47,15 @@ jobs:
           ./run-tests.sh --check-shellcheck
 
   lint-black:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
 
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: "3.8"
 
       - name: Check Python code formatting
         run: |
@@ -64,15 +64,15 @@ jobs:
           ./run-tests.sh --check-black
 
   lint-flake8:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
 
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: "3.8"
 
       - name: Check compliance with pep8, pyflakes and circular complexity
         run: |
@@ -81,15 +81,15 @@ jobs:
           ./run-tests.sh --check-flake8
 
   lint-pydocstyle:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
 
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: "3.8"
 
       - name: Check compliance with Python docstring conventions
         run: |
@@ -98,15 +98,15 @@ jobs:
           ./run-tests.sh --check-pydocstyle
 
   lint-check-manifest:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
 
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: "3.8"
 
       - name: Check Python manifest completeness
         run: |
@@ -115,15 +115,15 @@ jobs:
           ./run-tests.sh --check-manifest
 
   docs-sphinx:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3
 
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: "3.8"
 
       - name: Install system dependencies
         run: |
@@ -140,10 +140,10 @@ jobs:
         run: ./run-tests.sh --check-sphinx
 
   python-tests:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
-        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
 
     steps:
       - name: Checkout