readForwardFee misdescription

[Shvandre]

https://docs.tact-lang.org/ref/core-advanced/#contextreadforwardfee

It says that it reads forward fee from incoming message. But more accurate description could be
"It reads forwardFee from the incoming message and estimates forward + action fee" or smth like that.
(Because it actually multiplies forwardFee on 3/2 approx.)

[novusnota]

I've peeked into TON sources, and the note in code (and in TON Docs) on fwd_fee * 2^16 / first_frac is also incorrect. This happens instead: floor(fwd_fee * 2^16 / (2^16 - first_frac)).

I'll adjust docs of Context.readForwardFee() and getOriginalFwdFee().