Extend the documentation of `TwoQubitControlledUDecomposer`

[1ucian0]

In #16123 the class TwoQubitControlledUDecomposer got a big update, but its documentation didn't.

This issue should be closed with a PR updating the documentation accordantly, based on the details in PR #16123 . The PR must include a screenshot of the documentation page generated by tox -edocs.

[1ucian0]

❗ From June 3rd to 17th, this issue is participating in the 6th edition of unitaryHACK more info...

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