Test both PyPy3.6 and PyPy3.7

Co-authored-by: Thomas Grainger <[email protected]>

Author: hugovk

.github/workflows/test.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["pypy3", "3.6", "3.7", "3.8", "3.9"]
+        python-version: ["pypy-3.6", "pypy-3.7", "3.6", "3.7", "3.8", "3.9"]
         tox-extra-versions: [
             "pytest46-xdist127",
             "pytest46-xdist133",