Fux bug in functions.md example hypot (#54267)

In the section explaining the `return` key word, the example of the
function computing the hypotenuse length of a right triangle with sides
of length x and y should return `abs(x)` if y is zero, and not
`zero(x)`.

doc/src/manual/functions.md

@@ -174,7 +174,7 @@ julia> function hypot(x, y)
                return x*sqrt(1 + r*r)
            end
            if y == 0
-               return zero(x)
+               return x
            end
            r = x/y
            return y*sqrt(1 + r*r)