Improve docs for raw.to_data_frame

[1himan]

Reference issue (if any)

Fixes #12701

What does this implement/fix?

Additional information

Just a minor improvement for more clarity in the documentation.
An added notes section under raw.to_data_frame(), explicitly explaining the default behaviour of that api, which is to convert the data to SI units before returning it by default.

[1himan]

Do I have to describe the changes in the changelog as well, for such a minor change?

[tsbinns]

I would argue the unit conversion behaviour is already described in the scalings parameter description of to_data_frame.

Also, the note has it the wrong way around: data is stored internally in standard (SI) units (e.g., V for EEG data), but what the method returns is the data scaled into a more appropriate range (e.g., uV for EEG data).

[1himan]

I would argue the unit conversion behaviour is already described in the scalings parameter description of to_data_frame.

Also, the note has it the wrong way around: data is stored internally in standard (SI) units (e.g., V for EEG data), but what the method returns is the data scaled into a more appropriate range (e.g., uV for EEG data).

You're right. after reading more on this, I found out that this method doesn't do any "conversions" on data at all, rather it returns the data(picked channels) with scaling factors applied(default behaviour - scalings=None) which is useful for plotting.