No more Python 3.7

Author: djuarezg

.github/workflows/build.yml

@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: [3.7, 3.8, 3.9]
+        python-version: [3.8, 3.9]
         os: [ubuntu-latest]
         include:
           - python-version: 3.6