P.676 documentation

[esqt]

Hello!

There are a few mistakes in the documentation of P.676:

• In the slant_inclined_path_equivalent_height method, the argument p is described as a probability, whereas it should be a pressure (hPa). I believe it comes from the fact that the variable is lowercase, when pressure appears to use an uppercase letter P elsewhere in your code.

https://github.com/inigodelportillo/ITU-Rpy/blob/ab8e82dd46b018c7312ae8c5ced682664c9d594d/itur/models/itu676.py#L1446-L1447

• In the get_version method: it is refering to Rec. P.530.

https://github.com/inigodelportillo/ITU-Rpy/blob/ab8e82dd46b018c7312ae8c5ced682664c9d594d/itur/models/itu676.py#L1252-L1253

I can submit a pull request if needed.