Decrease size of GC heap to allow more DAL allocs (#2246)

libs/core/pxtcore.h

@@ -16,11 +16,8 @@ void debuglog(const char *format, ...);
 
 #define GC_MAX_ALLOC_SIZE 9000
 
-#if CONFIG_ENABLED(MICROBIT_BLE_ENABLED)
 #define GC_BLOCK_SIZE 256
-#else
-#define GC_BLOCK_SIZE 1000
-#endif
+#define NON_GC_HEAP_RESERVATION 1024
 
 #define DMESG NOLOG