CORTEX_MPU_M3_MPS2_QEMU_GCC: remove unused defines (FreeRTOS#1233)

From CORTEX_MPU_M3_MPS2_QEMU_GCC remove unused configNUM_TX_DESCRIPTORS
define and remove HEAP3 from as heap_4.c is used.

Signed-off-by: Florian La Roche <Florian.LaRoche@gmail.com>
Co-authored-by: Rahul Kar <118818625+kar-rahul-aws@users.noreply.github.com>

Author: laroche

FreeRTOS/Demo/CORTEX_MPU_M3_MPS2_QEMU_GCC/FreeRTOSConfig.h

@@ -72,7 +72,6 @@ extern void vAssertCalled( void );
 #define configUSE_COUNTING_SEMAPHORES                    1
 #define configSUPPORT_DYNAMIC_ALLOCATION                 1
 #define configSUPPORT_STATIC_ALLOCATION                  1
-#define configNUM_TX_DESCRIPTORS                         15
 #define configSTREAM_BUFFER_TRIGGER_LEVEL_TEST_MARGIN    2
 #define configCHECK_FOR_STACK_OVERFLOW                   2
 #define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS       0
@@ -134,9 +133,4 @@ unsigned long ulGetRunTimeCounterValue( void ); /* Prototype of function that re
 extern void vLoggingPrintf( const char * pcFormatString,
                             ... );
 
-#ifdef HEAP3
-    #define xPortGetMinimumEverFreeHeapSize    ( x )
-    #define xPortGetFreeHeapSize               ( x )
-#endif
-
 #endif /* FREERTOS_CONFIG_H */