Add cast for legacy max behavior returning boolean.

src/Statistics/Distance.php

@@ -493,7 +493,7 @@ public static function chebyshev(array $xs, array $ys): float
             throw new Exception\BadDataException('xs and ys must have the same number of elements');
         }
 
-        return \max(\array_map(
+        return (float) \max(\array_map(
             function (float $xᵢ, $yᵢ) {
                 return \abs($xᵢ - $yᵢ);
             },