Fix Android multi-window error message notation (#22350)

src/Core/src/Platform/Android/ApplicationExtensions.cs

@@ -52,7 +52,7 @@ public static void CreatePlatformWindow(this Activity activity, IApplication app
 				throw new InvalidOperationException(
 					$"This window is already associated with an active Activity ({oldActivity.GetType()}). " + 
 					$"Please override CreateWindow on {application.GetType()} "  + 
-					$"to add support for multiple activities https://aka.ms/maui-docs-create-window"  + 
+					$"to add support for multiple activities https://aka.ms/maui-docs-create-window "  + 
 					$"or set the LaunchMode to SingleTop on {activity.GetType()}.");
 			}