use updated pypy3 name for github actions (#685)

Author: asottile

.github/workflows/test.yml

@@ -8,13 +8,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "pypy3"]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "pypy-3.7"]
         os: [ubuntu-latest]
         # Include minimum py3 + maximum py3 + pypy3 on Windows
         include:
           - { os: "windows-latest" , python-version: "3.6" }
           - { os: "windows-latest" , python-version: "3.10" }
-          - { os: "windows-latest" , python-version: "pypy3" }
+          - { os: "windows-latest" , python-version: "pypy-3.7" }
 
     steps:
       - uses: actions/checkout@v2