Implement max_value to return the largest element of the array, walking it with pointer arithmetic
(arr + i / *p-style traversal) instead of arr[i] indexing – the point of this exercise is to make the
scores[i] == *(scores + i) equivalence from the lesson feel natural to write, not just to read.
arr here is a const int *, not int[] – this is the “array decays to a pointer” fact from the lesson made
visible in a function signature: once an array is passed as an argument, the parameter really is just a pointer
(plus, by convention, an explicit length alongside it, since sizeof can’t recover the original array’s size
from inside the function).