Update History.txt for V10.4.6

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>

Author: aggarg

History.txt

@@ -1,7 +1,15 @@
-Changes between FreeRTOS V10.4.5 and TBD
-
 Documentation and download available at https://www.FreeRTOS.org/
 
+Changes between FreeRTOS V10.4.6 and FreeRTOS V10.4.5
+
++ ARMv7-M and ARMv8-M MPU ports – prevent non-kernel code from calling the
+ internal functions xPortRaisePrivilege and vPortResetPrivilege by changing
+ them to macros.
++ Introduce a new config configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS which
+ enables developers to prevent critical sections from unprivileged tasks.
+ It defaults to 1 for backward compatibility. Application should set it to
+ 0 to disable critical sections from unprivileged tasks.
+
 Changes between FreeRTOS V10.4.4 and FreeRTOS V10.4.5 released September 10 2021
 
 See https://www.FreeRTOS.org/FreeRTOS-V10.4.5.html