ci: migrate deprecated grammar

Author: gengjiawen

.github/workflows/tests.yml

@@ -32,8 +32,8 @@ jobs:
       - name: Set Windows environment
         if: matrix.os == 'windows-latest'
         run:
-          echo '::set-env name=GYP_MSVS_VERSION::2015'
-          echo '::set-env name=GYP_MSVS_OVERRIDE_PATH::C:\\Dummy'
+          echo 'GYP_MSVS_VERSION=2015' >> $GITHUB_ENV
+          echo 'GYP_MSVS_OVERRIDE_PATH=C:\\Dummy' >> $GITHUB_ENV
       - name: Lint Python
         if: matrix.os == 'ubuntu-latest'
         run: |