Migrate github action to use environment files instead of set-output.

Updated the test workflow according to the instructions at https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Author: davidt

.github/workflows/test.yml

@@ -45,8 +45,7 @@ jobs:
 
     - name: Get pip cache dir
       id: pip-cache
-      run: |
-        echo "::set-output name=dir::$(pip cache dir)"
+      run: echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
 
     - name: Cache
       uses: actions/cache@v3