## Summary of Changes
Suppress
[warning](https://cgal.geometryfactory.com/CGAL/testsuite/CGAL-6.2-Ic-134/Lab_Demo/TestReport_lrineau_Ubuntu-latest-GCC6-CXX1z.gz)
issued by gcc.
```
include/CGAL/Three/Viewer_interface.h:42:21: warning: defining ‘CGAL::Three::Viewer_interface’, which previously failed to be complete in a SFINAE context [-Wsfinae-incomplete=]
42 | class VIEWER_EXPORT Viewer_interface : public CGAL::QGLViewer{
| ^~~~~~~~~~~~~~~~
```
## Release Management
* Affected package(s): Lab
* License and copyright ownership: unchanged
Sebastien Loriot
9ec37162fe