is_else_cause: don't use hir_parent_iter just to go one level up

[ada4a]

changelog: none

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[github-actions]

Lintcheck changes for d74fe2e

Lint	Added	Removed	Changed
clippy::branches_sharing_code	19	0	2
clippy::comparison_chain	1	0	0
clippy::if_not_else	21	0	4
clippy::if_then_some_else_none	16	0	1
clippy::manual_map	0	0	1
clippy::option_if_let_else	60	0	6

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