Update hashbrown requirement from 0.14 to 0.15 #228

Job	Run time
coverage (-C target-cpu=native, avx2, 128bit)	1m 32s
coverage (-C target-cpu=native, avx2, custom-types)	1m 23s
clippy_check (-C target-cpu=native, avx2, 128bit)	1m 24s
clippy_check (-C target-cpu=native, avx2, custom-types)	1m 17s
coverage (-C target-cpu=native, avx2, c-abi)	1m 45s
coverage (-C target-cpu=native, avx2, hashbrown)	1m 30s
clippy_check (-C target-cpu=native, avx2, c-abi)	1m 38s
clippy_check (-C target-cpu=native, avx2, hashbrown)	1m 19s
coverage (-C target-cpu=native, avx2, halfbrown)	1m 25s
clippy_check (-C target-cpu=native, avx2, halfbrown)	1m 13s
coverage (-C target-cpu=native -C target-feature=-avx2, sse, 128bit)	1m 29s
clippy_check (-C target-cpu=native -C target-feature=-avx2, sse, 128bit)	1m 16s
coverage (-C target-cpu=native -C target-feature=-avx2, sse, custom-types)	1m 33s
clippy_check (-C target-cpu=native -C target-feature=-avx2, sse, custom-types)	1m 20s
coverage (-C target-cpu=native -C target-feature=-avx2, sse, c-abi)	1m 49s
clippy_check (-C target-cpu=native -C target-feature=-avx2, sse, c-abi)	1m 39s
coverage (-C target-cpu=native -C target-feature=-avx2, sse, hashbrown)	1m 25s
coverage (-C target-cpu=native -C target-feature=-avx2, sse, halfbrown)	1m 28s
clippy_check (-C target-cpu=native -C target-feature=-avx2, sse, hashbrown)	1m 23s
clippy_check (-C target-cpu=native -C target-feature=-avx2, sse, halfbrown)	1m 24s
	29m 12s

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