Updated set-fact key

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

@@ -130,7 +130,7 @@
     mode: 0755
 
 - set_fact:
-    media_storage_providers: |
+    matrix_synapse_media_storage_providers: |
       {{
         matrix_synapse_media_storage_providers|default([])
         +