Reduce reserved heap size as it is not really used.

STM32L433CCUx_FLASH.ld

@@ -4,7 +4,7 @@ ENTRY(Reset_Handler)
 /* Highest address of the user mode stack */
 _estack = 0x2000C000;    /* end of RAM */
 /* Generate a link error if heap and stack don't fit into RAM */
-_Min_Heap_Size = 0x1000;      /* required amount of heap  */
+_Min_Heap_Size = 0x200;      /* required amount of heap  */
 _Min_Stack_Size = 0x400; /* required amount of stack */
 
 /* Specify the memory areas */