Fix buffer access

Author: kylebarron

rust/geoarrow/src/scalar/coord/scalar.rs

@@ -25,14 +25,14 @@ impl<'a> CoordTrait for Coord<'a> {
     }
 
     fn nth_unchecked(&self, n: usize) -> Self::T {
-        self.buffer.buffers[n][self.i * self.buffer.coords_stride]
+        self.buffer.buffers[n][self.i * self.buffer.coords_stride + n]
     }
 
     fn x(&self) -> Self::T {
         self.buffer.buffers[0][self.i * self.buffer.coords_stride]
     }
 
     fn y(&self) -> Self::T {
-        self.buffer.buffers[1][self.i * self.buffer.coords_stride]
+        self.buffer.buffers[1][self.i * self.buffer.coords_stride + 1]
     }
 }