sanitize_dataframe utilizes deprecated Pandas convert_dtype param

[cdkini]

This particular utility function uses a deprecated Pandas codepath: https://github.com/altair-viz/altair/blob/ec13a671d53419f371b629d449f719240d1f1756/altair/utils/core.py#L410C1-L410C76

As this emits a FutureWarning and will eventually be removed, could it be replaced with the suggestion?

FutureWarning: the convert_dtype parameter is deprecated and will be removed in a future version.  Do ``ser.astype(object).apply()`` instead if you want ``convert_dtype=False``.

Versions: Altair 4.2.2 and Pandas 2.1.0
OS: Darwin 22.6.0

[binste]

Thanks for reporting this @cdkini. Makes sense, I'll look into it.

For my own reference, it's deprecated since version 2.1 (search for convert_type)