remove read_excel keyword NotImplemented error, update documentation #11544
Followed up in #14326

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Towards fixing bug #11544, with respect to comments on merged PR #11870.

I've removed the `NotImplemented` error for `parse_dates` and `date_parser` keywords in `read_excel`, seeing that they are implemented (see discussion in #11870). I've added an example of the intended functionality in the documentation
