fix(forms): Update the typed forms migration to use FormArray<T> instead of FormArray<T[]>.

[dylhunn]

Previously, FormArray accepted an array generic. With the most up-to-date prototype, it accepts the element type, so the migration must be updated accordingly.

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[AndrewKushnir]

👍

[jessicajaniuk]

This has merge conflicts with 13.2.x. Updating to target: minor and merging. Please create a patch PR.

[jessicajaniuk]

This PR was merged into the repository by commit cae1e44.

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