Drop pypy3 from CI for now

The setup-python step seems to be failing, need to investigate this

Author: filmor

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        python: ['3.9', '3.8', '3.7', '3.6', pypy3]
+        python: ['3.9', '3.8', '3.7', '3.6'] # pypy3
 
     steps:
     - uses: actions/checkout@v2