docs: fix typo in multisig docs #6362

Job	Run time
build-linux-x86_64-post-merge	12m 37s
build-nightly-pre-merge	-1s
build-linux-x86_64-pre-merge	-1s
build-linux-x86_64-workflow-dispatch	-1s
documentation-tests	0s
upload-to-s3-workflow-dispatch	0s
local-env	0s
workflow-dispatch-flow-complete	0s
pre-merge-checks-complete	0s
upload-to-s3	56s
deploy-rustdoc	13m 56s
post-merge-actions-complete	4s
	27m 30s

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