updated content description to discourage using as a tempalte module

lib/ansible/modules/files/copy.py

@@ -43,6 +43,7 @@ options:
     version_added: "1.1"
     description:
       - When used instead of 'src', sets the contents of a file directly to the specified value.
+        This is for simple values, for anything complex or with formatting please switch to the template module.
     required: false
     default: null
   dest: