docs: fix admonition block closure in mobile-id API guide

Replace an incorrect markdown fence marker with the proper admonition terminator so the section renders correctly.

Author: phaupt

docs/rest-api-guide/mobile-id-api.md

@@ -847,7 +847,7 @@ In case a user has a too low location confidence score, the following points sho
       </MSS_Signature>
 
 ```
-
+:::
 
 ##### MSS Signature Response incl. Geofencing Location Data