Update links in thread_intro.md

Apply PR #866 to 5.11.

Author: Amanda Butler

docs/reference/technology/mesh/thread_intro.md

@@ -33,10 +33,10 @@ The key elements of Mbed OS are:
 
 Mbed Thread is implemented in the Nanostack library, which also supports the 6LoWPAN protocol. In Mbed OS, the Thread stack runs in its own RTOS thread using an internal event scheduler. Mbed OS provides the [Mesh C++ API](../apis/mesh-api.html) for building Thread applications.
 
-- To connect to the Thread network, use the [Thread interface API](https://github.com/ARMmbed/mbed-os/blob/master/features/nanostack/FEATURE_NANOSTACK/mbed-mesh-api/mbed-mesh-api/ThreadInterface.h).
+- To connect to the Thread network, use the [Mbed Mesh API](../apis/mesh-api.html) or [Thread interface API](https://github.com/ARMmbed/mbed-os/blob/master/features/nanostack/mbed-mesh-api/mbed-mesh-api/ThreadInterface.h).
 - For the socket communication over the Thread network, use the [Mbed sockets API](../apis/network-socket.html).
 
-Nanostack provides a set of C API headers with more functionalities. The [nanostack repository](https://github.com/ARMmbed/mbed-os/tree/master/features/nanostack/FEATURE_NANOSTACK/sal-stack-nanostack/nanostack) has the following header files():
+Nanostack provides a set of C API headers with more functionalities. The [nanostack repository](https://github.com/ARMmbed/mbed-os/tree/master/features/nanostack/sal-stack-nanostack/nanostack) has the following header files:
 
 - `thread_management_if.h` for initializing the stack and managing the network data.
 - `thread_commissioning_api.h` for implementing an on-mesh or a native Thread commissioner.