The current documentation for the `machine.RTC` class contains information
about the `RTC.cancel` method for cancelling pending alarms.
However only two ports (cc3200 and mimxrt) implement this functionality
but under a different name: `RTC.alarm_cancel`. The mimxrt port also
implements `RTC.cancel` but it is aliased to `RTC.alarm_cancel` anyway.
To maintain naming consistency, this commit updates the documentation to
officially define `RTC.alarm_cancel` as the method to call to cancel
pending alarms and deprecates mimxrt's `RTC.cancel` implementation.
`RTC.cancel` in the mimxrt port is thus scheduled for removal in
MicroPython v2.
Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
e8c3f31ba2