Add source option to docker_image to fix deprecation warning

roles/matrix-synapse/tasks/goofys/setup_install.yml

@@ -1,6 +1,7 @@
 - name: Ensure Goofys Docker image is pulled
   docker_image:
     name: "{{ matrix_s3_goofys_docker_image }}"
+    source: "pull"
 
 # This will throw a Permission Denied error if already mounted
 - name: Check Matrix Goofys external storage mountpoint path