Create a function that takes an array of non-negative integers and strings and return a new array without the strings.
filterArray([1, 2, "a", "b"]) ➞ [1, 2]
filterArray([1, "a", "b", 0, 15]) ➞ [1, 0, 15]
filterArray([1, 2, "aasf", "1", "123", 123]) ➞ [1, 2, 123]