fix matrix_synapse_sso.client_whitelist misconfiguration

roles/matrix-synapse/defaults/main.yml

@@ -464,5 +464,5 @@ matrix_synapse_oidc_config:
 
 # Set trusted SSO resources, e.g. [ "https://element.matrix.domain" ]
 matrix_synapse_sso:
-  client_whitelist: ["{{https://element.matrix.domain}}"]
+  client_whitelist: []