chore(docs): Use correct headline level for sw.window.getId (#1076)

Author: SebastianFranze

docs/admin-sdk/api-reference/window.md

@@ -66,24 +66,24 @@ No parameters required.
 #### Return value:
 Returns a promise without data.
 
-### Get an unique identifier for the window
+### Get a unique identifier for the window
 
 > Available since Shopware v6.7.1.0
 
 When it comes to session handling it can be useful to have a unique identifier for your window.
 
-### Usage:
+#### Usage:
 ```ts
 sw.window.getId() 
 ```
 
-### Parameters
+#### Parameters:
 No parameters required
 
-### Return value:
+#### Return value:
 A `string` representing an unique identifier for the current window
 
-### Example
+#### Example:
 In this example we check if the `sessionStorage` contains data from a former window. This can happen if a user uses the *Duplicate Tab* feature of some browsers.
 
 ```ts