Fix links

Author: chgeo

-exercises-/03-ConnectService/MockServer/README.md

@@ -41,4 +41,4 @@ The mock server provided by SAP S/4HANA Cloud SDK can be used to test the OData
 ## Next
 From here on, the application uses the server as if it would be a live SAP S/4HANA system.
 
-Continue with the [exercise](../README.MD).
+Continue with the [exercise](../README.md).

-exercises-/03-ConnectService/README.md

@@ -11,7 +11,7 @@ In this exercise you will learn how to add a remote service to your app that fet
 ## Exercise description
 
 ### 1. Setup Mock Server for SAP S/4HANA
-In case you do not have access to a live SAP S/4HANA system, there is a server that mocks the relevant OData APIs.  Follow [these instructions](MockServer/README.MD) to set it up.
+In case you do not have access to a live SAP S/4HANA system, there is a server that mocks the relevant OData APIs.  Follow [these instructions](MockServer/README.md) to set it up.
 
 ### 2. Switch to a different start branch