fix warning
```
In constructor ‘constexpr std::pair<_T1, _T2>::pair(_U1&&, _U2&&) [with _U1 = CGAL::Triangle_3<CGAL::Epick>; _U2 = bool; _T1 = CGAL::Triangle_3<CGAL::Epick>; _T2 = bool]’,
inlined from ‘constexpr std::pair<typename std::__strip_reference_wrapper<typename std::decay<_Tp>::type>::__type, typename std::__strip_reference_wrapper<typename std::decay<_Tp2>::type>::__type> std::make_pair(_T1&&, _T2&&) [with _T1 = CGAL::Triangle_3<CGAL::Epick>; _T2 = bool]’ at /usr/include/c++/15/bits/stl_pair.h:1169:72,
inlined from ‘std::pair<CGAL::Triangle_3<CGAL::Epick>, bool> CGAL::Epic_converter<IK>::operator()(const typename IK::Triangle_3&) const [with IK = CGAL::Simple_cartesian<CGAL::Interval_nt<false> >]’ at /mnt/testsuite/include/CGAL/Epic_converter.h:224:28:
/usr/include/c++/15/bits/stl_pair.h:464:11: warning: ‘<unnamed>’ may be used uninitialized [-Wmaybe-uninitialized]
464 | : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
-> Use the default constructor of the pair, instead of `make_pair`.
Laurent Rineau
79cb90d5e7