Fix typo in rustdoc of from_timestamp_nanos() #3437

Job	Run time
rust_versions (ubuntu-latest, stable)	56s
rust_versions (ubuntu-latest, beta)	48s
rust_versions (ubuntu-latest, nightly)	1m 19s
timezones (ubuntu-latest, ACST-9:30)	1m 30s
features_check (ubuntu-latest)	3m 45s
timezones (ubuntu-latest, EST4)	1m 20s
alternative_targets (ubuntu-latest, wasm32-unknown-emscripten)	26s
timezones (ubuntu-latest, UTC0)	1m 19s
alternative_targets (ubuntu-latest, aarch64-apple-ios)	19s
timezones (ubuntu-latest, Asia/Katmandu)	1m 22s
alternative_targets (ubuntu-latest, aarch64-linux-android)	13s
no_std (ubuntu-latest, thumbv6m-none-eabi)	12s
timezones (macos-latest, ACST-9:30)	1m 11s
no_std (ubuntu-latest, x86_64-fortanix-unknown-sgx)	9s
timezones (macos-latest, EST4)	37s
rust_msrv (ubuntu-latest)	58s
timezones (macos-latest, UTC0)	30s
timezones (macos-latest, Asia/Katmandu)	32s
test_wasm (ubuntu-latest)	19s
timezones (windows-latest, ACST-9:30)	2m 24s
check-docs	19s
timezones (windows-latest, EST4)	2m 14s
cross-targets (x86_64-unknown-illumos)	1m 10s
cross-tests (ubuntu-latest)	1m 45s
timezones (windows-latest, UTC0)	3m 5s
test_wasi (ubuntu-latest, wasm32-wasi)	26s
timezones (windows-latest, Asia/Katmandu)	2m 10s
	31m 18s

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