Match micro:bit MicroPython version. (#77)

Would be nice to automate but this will do for now.

Author: microbit-matt-hillsdon

src/mpconfigport.h

@@ -100,7 +100,7 @@
     { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&mp_builtin_open_obj) },
 #endif
 
-#define MICROBIT_RELEASE "2.0.0"
+#define MICROBIT_RELEASE "2.1.0"
 #define MICROBIT_BOARD_NAME "micro:bit"
 #define MICROPY_HW_BOARD_NAME MICROBIT_BOARD_NAME " v" MICROBIT_RELEASE
 #define MICROPY_HW_MCU_NAME "nRF52833"