Typo fix in RTC.c to fix rp2040 chip name

Author: KeithTheEE

shared-bindings/rtc/RTC.c

@@ -73,7 +73,7 @@ MP_PROPERTY_GETSET(rtc_rtc_datetime_obj,
 //|
 //|     A positive value speeds up the clock and a negative value slows it down.
 //|
-//|     **Limitations:** Calibration not supported on SAMD, Nordic, RP240, Spresense, and STM.
+//|     **Limitations:** Calibration not supported on SAMD, Nordic, RP2040, Spresense, and STM.
 //|
 //|     Range and value is hardware specific, but one step is often approximately 1 ppm::
 //|