Remove date code no longer needed since arrow-rs PR 2031 merge

[avantgardnerio]

Which issue does this PR close?

Closes this comment #3110 (comment)

Rationale for this change

We added code that is no longer needed, thanks to upstream merges in arrow-rs & chrono

What changes are included in this PR?

Removal of temporary code.

Are there any user-facing changes?

The requirement to have a newer chrono.

[avantgardnerio]

@alamb heads up!

[alamb]

Looks great -- the CI hasn't yet run on this PR, but when it does I am feeling good about it 👍

[alamb]

🤔 github claims it has conflicts -- maybe it needs a rebase against master?

[avantgardnerio]

thinking github claims it has conflicts -- maybe it needs a rebase against master?

Unfortunately due to the implementation of this:

https://github.com/apache/arrow-datafusion/blob/15a9a4becc4bb41262b10f1d5395fc1d026de753/datafusion/physical-expr/src/expressions/datetime.rs#L295

I think we have to wait for this:

chronotope/chrono#778

So that we can do this:

fn do_date_math<D>(prior: D, scalar: &ScalarValue, sign: i32) -> Result<D>
where
    D: Datelike + Add<Duration, Output = D> + Add<Months, Output = D>,