docs(api): use the memory update field names the route reads (#19279)

Fix Update Memory API docs — permission → permissions, system_promot → system_prompt. The route reads permissions/system_prompt; docs were wrong. Dataset endpoints keep permission (correct there).

docs/references/python_api_reference.md

@@ -2318,7 +2318,7 @@ Configurations to update. Available configurations:
 
   - Maximum 65535 characters
 
-- `permission`:  `enum<string>`, *Optional*
+- `permissions`:  `enum<string>`, *Optional*
 
   The updated memory permission. Available options: