Possibly redundant delay in `Rtc::sleep`

[dimpolo]

I'm unclear about the purpose of the 100ms delay before going to sleep here:

https://github.com/liebman/esp-hal/blob/2e2d67f315d7c3abf0d023fda541473858769965/esp-hal-common/src/rtc_cntl/mod.rs#L319C32-L319C32

@liebman suggested it might have been left in by mistake https://github.com/esp-rs/esp-hal/pull/574#issuecomment-1848601616

If so, we should remove the delay parameter of the various sleep methods