Fix missing allow-empty tag on ECS and Consul Catalog providers

Co-authored-by: Kevin Pollet <pollet.kevin@gmail.com>

docs/content/providers/ecs.md

@@ -13,18 +13,15 @@ Attach labels to your ECS containers and let Traefik do the rest!
     
     ```toml tab="File (TOML)"
     [providers.ecs]
-      clusters = ["default"]
     ```
     
     ```yaml tab="File (YAML)"
     providers:
-      ecs:
-        clusters:
-          - default
+      ecs: {}
     ```
     
     ```bash tab="CLI"
-    --providers.ecs.clusters=default
+    --providers.ecs=true
     ```
 
 ## Policy