feat!(iota): remove MultiSigCombinePartialSigLegacy #5973

Job	Run time
changes	9s
diff	8s
iota-sdk-changes	8s
license-check	0s
release-notes-check	8s
cargo-deny (advisories, licenses, bans, ...)	43s
clippy	3m 4s
move-test	0s
rustfmt	7s
test-extra (self-hosted)	11m 44s
graphql-rpc	15m 12s
cutting a new execution layer	1m 25s
Test iota-sdk	0s
Test iota	3m 44s
	36m 32s

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