Workaround CUDA warning.

[trivialfis]

cc @rongou

[trivialfis]

/home/jiaming/Workspace/XGBoost/xgboost/tests/cpp/data/../../../src/data/array_interface.h(540): warning #20011-D: calling a __host__ function("auto xgboost::ArrayInterface<(int)2, (bool)0> ::Initialize(const     ::std::map<   ::std::__cxx11::basic_string<char,     ::std::char_traits<char> , ::std::allocator<char> > ,  ::xgboost::Json,     ::std::less<void> , ::std::allocator<    ::std::pair<const    ::std::__cxx11::basic_string<char,     ::std::char_traits<char> , ::std::allocator<char> > ,  ::xgboost::Json> > >  &)::[lambda(const T1 *) (instance 1)]::operator ()<unsigned long> (const T1 *) const") from a __host__ __device__ function("xgboost::ArrayInterface<(int)2, (bool)0> ::DispatchCall< ::xgboost::ArrayInterface<(int)2, (bool)0> ::Initialize(const     ::std::map<   ::std::__cxx11::basic_string<char,     ::std::char_traits<char> , ::std::allocator<char> > ,  ::xgboost::Json,     ::std::less<void> , ::std::allocator<    ::std::pair<const    ::std::__cxx11::basic_string<char,     ::std::char_traits<char> , ::std::allocator<char> > ,  ::xgboost::Json> > >  &)   ::[lambda(const T1 *) (instance 1)]>  const") is not allowed

[rongou]

Is the warning still there? CUDA seems to be pretty picky about using a lambda.

[trivialfis]

it's removed.