[gimp] Fixed copy paste error in gimp_vector3_copy

[Michael Natterer <mitch src gnome org>]

commit fc0d2d9ce75b521ad03fd78d816a96174e49702d
Author: qarmin <mikrutrafal54 gmail com>
Date:   Thu Apr 30 15:19:39 2020 +0200

    Fixed copy paste error in gimp_vector3_copy

 libgimpmath/gimpvector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/libgimpmath/gimpvector.c b/libgimpmath/gimpvector.c
index d97622b624..28cc6654c0 100644
--- a/libgimpmath/gimpvector.c
+++ b/libgimpmath/gimpvector.c
@@ -1168,7 +1168,7 @@ gimp_vector3_copy (gpointer boxed)
   new_v = g_slice_new (GimpVector3);
   new_v->x = vector->x;
   new_v->y = vector->y;
-  new_v->y = vector->z;
+  new_v->z = vector->z;
 
   return new_v;
 }