Update example in lorawan.md

Point example to latest version.

Author: Amanda Butler

docs/api/lorawan/lorawan.md

@@ -14,7 +14,7 @@ To configure this class, please see the [LoRa configuration documentation](/docs
 
 Please visit our Arm Mbed Online Compiler example, and follow the instructions in the `README.md`.
 
-[![View code](https://www.mbed.com/embed/?url=https://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-lorawan/)](https://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-lorawan/file/ceea78461fbd/main.cpp)
+[![View code](https://www.mbed.com/embed/?url=https://github.com/ARMmbed/mbed-os-example-lorawan)](https://github.com/ARMmbed/mbed-os-example-lorawan/blob/master/main.cpp)
 
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