Update README to reflect method name change

The method name referenced in the code examples of the README file was changed from 'getCustomers()' to 'getAllCustomers()'. This change edits the instruction in the README to match the new method name, making the documentation accurate and up-to-date.

README.md

@@ -10,7 +10,7 @@ handlers that will be invoked in various situations, e.g. when the server return
 
 ### Example
 
-Example: assume that `myEndpoints` defines a method called `getCustomers()`:
+Example: assume that `myEndpoints` defines a method called `getAllCustomers()`:
 
 ```java
 public interface MyService {