Oh, balls. There isn't a geometrical shape in the world that hasn't been used as a symbol for something since antiquity.
There are two questions here:
(1) Is "Wicca" the ancient religion of the pre-Christian British Isles, or a new invention of a recent vintage? The answer is: a new invention.
(2) Was the ancient religion of the pre-Christian British Isles ever known to use "pentacles" as a symbol, or are the earliest documented users of this geometrical pattern Mediterranean Jewish students of the Zohar? Answer: the first people to use this symbol were of a different religion than the pre-Christian British and lived almost one thousand years after them.