Update python testing workflow configuration

The changes in the configuration file for the Python testing workflow include reducing the maximum parallel jobs from 7 to 6. The range of Python versions tested against has also been expanded to include 3.7, and all versions

.github/workflows/python_testing.yml

@@ -7,10 +7,10 @@ jobs:
 
     runs-on: ubuntu-latest
     strategy:
-      max-parallel: 7
+      max-parallel: 6
       fail-fast: False
       matrix:
-        python-version: [3.8, 3.9, 3.10, 3.11, 3.12, pypy3]
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
 
     steps:
     - uses: actions/checkout@v1