Fix link in SharedPtr.md

Fix broken link to build engine.

Author: Amanda Butler

docs/reference/api/platform/SharedPtr.md

@@ -11,7 +11,7 @@ When `ptr` is passed around by a value, the copy constructor and destructor mana
 
 ### SharedPtr class reference
 
-[![View code](https://www.mbed.com/embed/?type=library)](https://os-doc-builder.test.mbed.com/docs/development/mbed-os-api-doxy/class_shared_ptr.html)
+[![View code](https://www.mbed.com/embed/?type=library)](http://os-doc-builder.test.mbed.com/docs/development/mbed-os-api-doxy/class_shared_ptr.html)
 
 ### Shared pointer example