Update USE_CASES.md

Fix missing code in the use case for sending multiple emails to multiple recipients.

Author: Niladri24dutta

USE_CASES.md

@@ -351,7 +351,7 @@ namespace Example
                                                                        htmlContent
                                                                        );
             var response = await client.SendEmailAsync(msg);  
-                                                                     
+
         }
     }
 }
@@ -439,6 +439,7 @@ namespace Example
                                                                           htmlContent,
                                                                           substitutions
                                                                           );
+            var response = await client.SendEmailAsync(msg);                                                            
         }
     }
 }