chore(example): update flutter_quill_extensions to the latest

Author: EchoEllet

example/pubspec.lock

@@ -232,7 +232,7 @@ packages:
       path: "../flutter_quill_extensions"
       relative: true
     source: path
-    version: "11.0.0-dev.4"
+    version: "11.0.0-dev.6"
   flutter_quill_test:
     dependency: "direct dev"
     description: