Fix alignment errors in hashtable fuzzer #25549

Job	Run time
check_docs	1m 3s
check_update	1m 17s
address_ub_sanitizer	11m 37s
basic_clang	6m 5s
basic_gcc	7m 34s
check-ansi	2m 39s
fuzz_tests	3m 2s
minimal	2m 42s
no-deprecated	6m 7s
non-caching	16m 19s
no-shared-macos (macos-13)	6m 55s
no-shared-macos (macos-14)	4m 23s
no-shared-ubuntu	6m 32s
self-hosted (freebsd-13.2)	14m 31s
self-hosted (ubuntu-arm64-22.04)	33m 18s
enable_non-default_options	5m 17s
external-test-cf-quiche	3m 40s
external-test-pyca (1.51.0, 3.9)	6m 59s
external-tests	10m 48s
full_featured	6m 18s
legacy	5m 25s
memory_sanitizer	20m 5s
no-legacy	6m 1s
out-of-readonly-source-and-install-macos (macos-13)	12m 59s
out-of-readonly-source-and-install-ubuntu	8m 56s
out-of-readonly-source-and-install-macos (macos-14)	6m 30s
threads_sanitizer	6m 36s
	3h 43m 38s

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