Don't use deprecated method in `impl Arbitrary for DateTime` #2838

Job	Run time
features_check (ubuntu-latest)	5m 34s
rust_versions (ubuntu-latest, stable)	58s
features_check (macos-latest)	17m 11s
rust_msrv (ubuntu-latest)	54s
rust_versions (ubuntu-latest, beta)	1m 10s
rust_versions (ubuntu-latest, nightly)	1m 1s
features_check (windows-latest)	9m 2s
check-docs	21s
cross-tests (ubuntu-latest)	1m 47s
cross-targets (x86_64-sun-solaris)	1m 14s
alternative_targets (ubuntu-latest, wasm32-unknown-emscripten)	37s
alternative_targets (ubuntu-latest, aarch64-apple-ios)	16s
no_std (ubuntu-latest, thumbv6m-none-eabi)	9s
test_wasi (ubuntu-latest, wasm32-wasi)	24s
alternative_targets (ubuntu-latest, aarch64-linux-android)	10s
no_std (ubuntu-latest, x86_64-fortanix-unknown-sgx)	23s
test_wasm (ubuntu-latest)	22s
timezones (ubuntu-latest, ACST-9:30)	1m 13s
timezones (ubuntu-latest, EST4)	1m 18s
timezones (ubuntu-latest, UTC0)	1m 15s
timezones (ubuntu-latest, Asia/Katmandu)	1m 13s
timezones (macos-latest, ACST-9:30)	1m 10s
timezones (macos-latest, EST4)	1m 16s
timezones (macos-latest, UTC0)	1m 27s
timezones (macos-latest, Asia/Katmandu)	1m 13s
timezones (windows-latest, ACST-9:30)	2m 10s
timezones (windows-latest, EST4)	2m 2s
timezones (windows-latest, UTC0)	2m 25s
timezones (windows-latest, Asia/Katmandu)	2m 54s
	1h 1m 9s

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