cad/OrcaSlicer: Fix 32-bit build
LayerResult's second field is typed size_t, so std::numeric_limits::max
should also use size_t and not something related to coordinates for the
layer_id.
Reported by: pkg-fallout
Approved by: arrowd (co-mentor)
(cherry picked from commit b403418f4721af9ec4b2158539536e19ee564150)