Updated History.txt for task notification array change (FreeRTOS#65)

Updated History.txt to note the single task notification per task has been replaced with an array of task notifications per task.

Author: RichardBarry

History.txt

@@ -4,8 +4,10 @@ Changes between FreeRTOS V10.3.0 and FreeRTOS V10.3.1 released February 18 2020
 
 	See http://www.FreeRTOS.org/FreeRTOS-V10.3.x.html
 
-	./FreeRTOS-Labs directory was removed from this file. The libraries it 
+	+ ./FreeRTOS-Labs directory was removed from this file. The libraries it
 	contained are now available as a separate download.
+	+ Replaced the single task notification per task with an array of
+	notificatinos per task.
 
 Changes between FreeRTOS V10.2.1 and FreeRTOS V10.3.0 released February 7 2020