migrate set-output to the environment file (#1368)

.github/workflows/test.yml

@@ -20,6 +20,7 @@ jobs:
         id: set-matrix
         run: |
           import json
+          import os
           go = [
               # Keep the most recent production release at the top
               '1.19',
@@ -55,7 +56,8 @@ jobs:
               'include': includes
           }
           output = json.dumps(matrix, separators=(',', ':'))
-          print('::set-output name=matrix::{0}'.format(output))
+          with open(os.environ["GITHUB_OUTPUT"], 'a', encoding="utf-8") as f:
+              f.write('matrix={0}\n'.format(output))
         shell: python
   test:
     needs: list