[CI] Removes Python 3.6 from tests matrix and re-introduces Python 3.7

> See <https://github.blog/changelog/2025-01-15-github-actions-ubuntu-20-runner-image-brownout-dates-and-other-breaking-changes/>

Author: HorlogeSkynet

.github/workflows/integration.yml

@@ -16,6 +16,7 @@ jobs:
           - 'macOS-latest'
           - 'ubuntu-latest'
         python-version:
+          # - '3.6'
           # - '3.7'
           # - '3.8'
           - '3.9'
@@ -26,8 +27,8 @@ jobs:
           - '3.14-dev'
           - 'pypy3.9'
         include:
-          - os: 'ubuntu-20.04'
-            python-version: '3.6'
+          - os: 'ubuntu-22.04'
+            python-version: '3.7'
 
     steps:
       - uses: actions/checkout@v5