Drop unused mach time headers
Drop unused mach time headers

Summary:
> Now that we're no longer special-casing clock usage for MacOS, we're
> not referencing anything defined in these headers.

This is a backport of Core [[https://github.com/bitcoin/bitcoin/pull/18229 | PR18229]]

Depends on D8774

Test Plan:
`ninja all check-all`

@bot build-osx

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8776

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