Build docs with Python 3.7

Since we use Python 3.8 everywhere, let's use it there too.

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

.github/workflows/docs.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.7]
+        python-version: [3.8]
 
     steps:
       - name: Checkout code