fixed etching tank not accepting etching acid

src/main/java/me/desht/pneumaticcraft/common/block/entity/processing/EtchingTankBlockEntity.java

@@ -321,7 +321,7 @@ private class EtchingFluidTank extends SmartSyncTank {
 
         @Override
         public boolean isFluidValid(FluidStack stack) {
-            return FluidStack.isSameFluidSameComponents(EmptyPCBItem.getEtchingFluid(), fluidStack);
+            return stack.getFluid().isSame(EmptyPCBItem.getEtchingFluid().getFluid());
         }
     }
 }