Switch back to container-friendly path var

Resolves #55

Author: rossjrw

action.yml

@@ -111,7 +111,7 @@ runs:
 
     - name: Determine action version
       run: |
-        action_version=$("${{ github.action_path }}/lib/find-current-git-tag.sh" -p $actionrepo -f $actionref)
+        action_version=$("$GITHUB_ACTION_PATH/lib/find-current-git-tag.sh" -p $actionrepo -f $actionref)
         echo "action_version=$action_version" >> "$GITHUB_ENV"
       shell: bash