Update README.md

Clean up.

Author: yuxin-azrtos

README.md

@@ -45,9 +45,9 @@ The following ZIP files can be downloaded from the [release](https://github.com/
 
 The [MXChip AZ3166 IoT DevKit](https://aka.ms/iot-devkit) is currently supported by the [getting-started](https://github.com/azure-rtos/getting-started/tree/master/MXChip/AZ3166) guide.
 
-## MS Learn and book samples
+## MS Learn samples
 
-Samples for MS Learn ThreadX course and [Real-Time Embedded Multithreading With ThreadX <sup>3rd edition</sup>](https://www.amazon.in/Real-time-Embedded-Multithreading-Using-Threadx/dp/1523730420) can be built and run on Windows using Visual Studio.
+Samples for MS Learn ThreadX course can be built and run on Windows using Visual Studio.
 
 -   [Azure_RTOS_6.1_Win32_Samples_2020_10_18.zip](https://github.com/azure-rtos/samples/releases/download/v6.1_rel/Azure_RTOS_6.1_Win32_Samples_2020_10_18.zip)