I'm not aware of a single word, but you could say that you are changing a multiset into a true set.
From Wikipedia:
A set is a gathering together into a whole of definite, distinct
objects... every element of a set must be unique; no two members may
be identical.
In mathematics, the notion of multiset (or bag) is a
generalization of the notion of set in which members are allowed to
appear more than once.
Where did you get the word uniquate? I couldn't find it anywhere.
If it's indeed an invented term, and you were writing a paper, you could define uniquate as an operation that changes a bag, or multiset, into a true set, and then use that term in subsequent places in the paper where you want to describe that operation. You could even go further, and specify that the number of elements in the original multiset must remain constant:
We define uniquate as an operation that changes a bag, or
multiset, into a true set, by replacing (not removing) any duplicate
elements.
Then, later in the paper:
The next step of the process is to uniquate Bag B into Set B.
But I wouldn't use the word outright, without defining it first. (Even if it is a real word, it appears rare enough that a formal definition within the document would be warranted).