BUG: Make/files: use C style comment

src/fvOptions/Make/files

@@ -33,8 +33,10 @@ $(derivedSources)/solidificationMeltingSource/solidificationMeltingSource.C
 $(derivedSources)/solidificationMeltingSource/solidificationMeltingSourceIO.C
 $(derivedSources)/tabulatedAccelerationSource/tabulatedAccelerationSource.C
 $(derivedSources)/tabulatedAccelerationSource/tabulated6DoFAcceleration/tabulated6DoFAcceleration.C
-//$(derivedSources)/directionalPressureGradientExplicitSource/directionalPressureGradientExplicitSource.C
-//$(derivedSources)/directionalPressureGradientExplicitSource/directionalPressureGradientExplicitSourceIO.C
+/*
+$(derivedSources)/directionalPressureGradientExplicitSource/directionalPressureGradientExplicitSource.C
+$(derivedSources)/directionalPressureGradientExplicitSource/directionalPressureGradientExplicitSourceIO.C
+*/
 $(derivedSources)/buoyancyForce/buoyancyForce.C
 $(derivedSources)/buoyancyForce/buoyancyForceIO.C
 $(derivedSources)/buoyancyEnergy/buoyancyEnergy.C