Update deploy action to version 3

Author: Jawnnypoo

.github/workflows/deploy.yml

@@ -35,9 +35,9 @@ jobs:
 
     - id: 'deploy'
       name: 'deploy'
-      uses: 'google-github-actions/deploy-appengine@v0'
+      uses: 'google-github-actions/deploy-appengine@v3'
       with:
         project_id: 'skyhookapi'
 
     - name: 'show output'
-      run: 'echo ${{ steps.deploy.outputs.url }}'
+      run: 'echo ${{ steps.deploy.outputs.url }}'