vector2d: use slice instead of Vec

Signed-off-by: Matej Focko <mfocko@redhat.com>

src/vector2d.rs

@@ -33,7 +33,7 @@ where
     &v[y][x]
 }
 
-pub fn in_range<T, U>(v: &Vec<Vec<U>>, idx: &Vector2D<T>) -> bool
+pub fn in_range<T, U>(v: &[Vec<U>], idx: &Vector2D<T>) -> bool
 where
     usize: TryInto<T>,
     <usize as TryInto<T>>::Error: Debug,