Actually release Python 3.9

.github/workflows/appimage.yml

@@ -60,7 +60,7 @@ jobs:
     if: github.ref == 'refs/heads/master'
     strategy:
       matrix:
-        version: [2.7, 3.5, 3.6, 3.7, 3.8]
+        version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/download-artifact@v1