Remove obsolete Chrono header

Author: rserban

src/hydro/hydro_system.cpp

@@ -33,7 +33,6 @@
 #include <chrono/physics/ChSystemSMC.h>
 #include <chrono/physics/ChLoadHydrodynamics.h>
 #include <chrono/solver/ChIterativeSolverLS.h>
-#include <chrono/solver/ChSolverPMINRES.h>
 #include <chrono/timestepper/ChTimestepper.h>
 #include <chrono/timestepper/ChTimestepperHHT.h>
 #include <chrono/fea/ChMeshFileLoader.h>