sync release versions for v1.15.6 #102

Job	Run time
compute-hash (x86_64-linux, blacksmith-4vcpu-ubuntu-2404)	11h 10m 39s
compute-hash (aarch64-darwin, macos-latest)	9m 36s
compute-hash (x86_64-darwin, macos-15-intel)	15m 41s
compute-hash (aarch64-linux, blacksmith-4vcpu-ubuntu-2404-arm)	11h 10m 39s
update-hashes	1s
	22h 46m 36s

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