Fix const qualifier warning on BaseGDObject::cast_from_variant

Author: touilleMan

src/godot/classes.pxd.j2

@@ -13,8 +13,11 @@ cdef class BaseGDObject:
         ret._gd_ptr = obj
         return ret #}
 
+    # TODO: In theory we should pass a `const gd_variant_t *gdvar` since the variant
+    # is not modified, however `GDExtensionTypeFromVariantConstructorFunc` doesn't
+    # specified a const to the variant parameter...
     @staticmethod
-    cdef inline object cast_from_variant(const gd_variant_t *gdvar):
+    cdef inline object cast_from_variant(gd_variant_t *gdvar):
         cdef gd_object_t obj = gdapi.gd_object_from_variant(gdvar)
         if obj == NULL:
             return None