Update Python in CI

Signed-off-by: Mihai Todor <todor@ebi.ac.uk>

Author: mihaitodor

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.7]
+        python-version: [3.9]
 
     steps:
     - uses: actions/checkout@v2