ENTST-545: remove unused GiftArticle code

[abshirahmed]

This PR deleted the old gift-article code now that the rebranded version is live. This is a follow on from https://github.com/Financial-Times/x-dash/pull/724.

The new gift article modal is now live in production. As part of the development for this rebranded version, we worked from a v2 directory in the code. This PR moves the v2 code to the root of the src directory, replacing the old gift-article code.

There are no functional changes in this PR.

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