remove fxhash example and dep #425

Job	Run time
nostd_build (1.63.0, thumbv6m-none-eabi)	1m 46s
miri	4m 46s
nostd_build (stable, thumbv6m-none-eabi)	19s
Check MSRV and minimal-versions	2m 2s
clippy	16s
tests (1.63.0)	2m 14s
tests (stable, arbitrary)	39s
tests (stable, quickcheck)	41s
tests (stable, rayon)	46s
tests (stable, rustc-rayon)	47s
tests (stable, serde)	47s
tests (stable, borsh)	39s
tests (stable, std)	37s
tests (beta)	39s
tests (nightly, test build benchmarks)	35s
Success	1s
	17m 34s

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