ci: Remove python 2.7 (woops, missed in #306)

Author: tony

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["2.7", "3.x"]
+        python-version: ["3.x"]
         tmux-version: ["2.6", "2.7", "2.8", "3.0a", "3.1b", "master"]
     steps:
       - uses: actions/checkout@v1