[BUG]: unused `xtol` argument in `ghi_from_poa_driesse_2023`

[echedey-ls]

Describe the bug
In function pvlib.irradiance.ghi_from_poa_driesse_2023 the argument xtol is unused.
However, in the docstring it is specified.

Seems like a typo.

To Reproduce
N/A

Expected behavior
To be used.

Screenshots
N/A

Versions:

• pvlib.__version__: latest
• pandas.__version__: N/A
• python: N/A

Additional context
I'll open a PR in short.