build: Drop Python 3.7

EOL Ended 2 months and 1 week ago (27 Jun 2023)

Author: tony

.github/workflows/tests.yml

@@ -14,9 +14,9 @@ jobs:
         tmux-version: [ '2.6', '2.7', '2.8', '3.0a', '3.1b', '3.2a', '3.3a', 'master' ]
         # balance ci coverage across supported python/tmux versions with CI speed
         include:
-          - python-version: '3.7'
+          - python-version: '3.8'
             tmux-version: '2.6'
-          - python-version: '3.7'
+          - python-version: '3.8'
             tmux-version: 'master'
     steps:
     - uses: actions/checkout@v3