There is a tradition of a St. Grace who was martyred in the 4th century, there is also a tradition of a St. Gracia of Lerida who was martyred in the 11th century (feast day June 1).
However even without those two traditions, canon law does not require the name of a Saint for baptism:
Can. 855 Parents, sponsors, and the pastor are to take care that a name foreign to Christian sensibility is not given.
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