NVStore - remove Thread.h include

As this include is not actually needed. Having it will cause issues
with the bootloader, as this will cause a need to get the full
CMSIS/RTOS package etc., which would bloat the bootloader size.

features/nvstore/source/nvstore.cpp

@@ -23,7 +23,6 @@
 #include "FlashIAP.h"
 #include "mbed_critical.h"
 #include "mbed_assert.h"
-#include "Thread.h"
 #include "mbed_wait_api.h"
 #include <algorithm>
 #include <string.h>