lattice_search: give Niggli character 40 its own reindex matrix

Character 40 carried a verbatim copy of character 35's matrix
(0-10 / -100 / 00-1), whose determinant is 1. A C-centred conventional
cell needs determinant 2, so a genuine oC lattice was returned as its
primitive monoclinic cell while still being labelled Orthorhombic 'C':
the refiner then clamped a ~117 degree beta to 90 and prediction dropped
half the reflections of a cell that has no centring.

International Tables A 3.1.3.1 gives 0-10 / 012 / -100 for character 40.
Character 35 is correct as it stands and is left alone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

image_analysis/lattice_search/LatticeSearch.cpp

@@ -238,7 +238,7 @@ LatticeSearchResult LatticeSearch(const CrystalLattice &L, double dist_tolerance
         {
             40, 2,
             false, false, -B / 2, 0, 0, false, false,
-            {0, -1, 0, -1, 0, 0, 0, 0, -1},
+            {0, -1, 0, 0, 1, 2, -1, 0, 0},
             gemmi::CrystalSystem::Orthorhombic, 'C'
         },
         {