extend/os/linux/formula_installer: use typed: strict

[p-linnane]

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Part of #17297.

[issyl0]

Ah, sorry! I should have explained and not assume you saw the PR yesterday where I switched these over. The point of rubocop:disable here (as opposed to :todo) is that these are not typecheckable because they use undef.

Unless you can confidently answer #17998 for this undef, it's better for now to focus on the rubocop:todos.

[carlocab]

Yea, let's do this now: #17998 (comment)