Fixed nvcc compile warnings for default constructor

[steimich96]

Fixes unnecessary compile warnings on nvcc.

dependencies/glm/glm/./ext/../detail/.././ext/../detail/type_mat4x2.hpp(36): warning #20012-D: __host__ annotation is ignored on a function("mat") that is explicitly defaulted on its first declaration
    __attribute__((device)) __attribute__((host)) constexpr mat() = default;

This was previously already adressed in #1107. I am not entirely sure if this was just an oversight or if this was intended, but it still leads to warnings.

Also see this stackoverflow post for further discussion.