chore: bump `stark-backend` tag #614

Job	Run time
extension-tests (rv32im, rv32im)	3m 10s
extension-tests (native, native)	3m 25s
extension-tests (keccak256, keccak256)	2m 6s
extension-tests (sha256, sha256)	1m 59s
extension-tests (bigint, bigint)	2m 49s
extension-tests (algebra, algebra)	2m 13s
extension-tests (ecc, ecc)	3m 33s
extension-tests (pairing, pairing)	3m 10s
	22m 25s

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