remove problematic pypy ci build, shrug

Author: irmen

.github/workflows/main-ci.yml

@@ -17,9 +17,8 @@ jobs:
 
     runs-on: ubuntu-latest
     strategy:
-      max-parallel: 4
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10', 'pypy-3.7']
+        python-version: ['3.7', '3.8', '3.9', '3.10']
 
     steps:
       - name: Checkout source