ENH: (andy as mattijs) header file clean-up

applications/solvers/compressible/rhoCentralFoam/BCs/U/maxwellSlipUFvPatchVectorField.C

@@ -28,8 +28,7 @@ License
 #include "mathematicalConstants.H"
 #include "fvPatchFieldMapper.H"
 #include "volFields.H"
-#include "surfaceFields.H"
-#include "fvCFD.H"
+#include "fvcGrad.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //