[T/M] Temporary disable Guenther-Salzer triax

due to instability: simulation is randomly hitting a non-convergence
point in local Newton at around time steps 100-125, t 0.22-0.23s,
with step size 0.001-0.002.

ProcessLib/SmallDeformation/Tests.cmake

@@ -101,7 +101,7 @@ if (OGS_USE_MFRONT)
     OgsTest(PROJECTFILE Mechanics/Ehlers/MFront/two_material_ids_single_solid.prj RUNTIME 1)
     if(NOT OGS_USE_MPI)
         OgsTest(PROJECTFILE Mechanics/GuentherSalzer/model_uniaxial_test.prj)
-        OgsTest(PROJECTFILE Mechanics/GuentherSalzer/model_triaxial_test.prj RUNTIME 100)
+        # OgsTest(PROJECTFILE Mechanics/GuentherSalzer/model_triaxial_test.prj RUNTIME 100) TODO (tnagel) Disabled due to instability.
     endif()
     OgsTest(PROJECTFILE Mechanics/PLLC/uniax_compression.prj)