PvtLiveGas: do not special case in the extrapolation code

at least, don't special case that much. This caused a discrepancy with
the opm-material PVT relations for Norne after 23 report steps. (which
takes an hour or two to get to with debugging options on my machine.)
As you can probably imagine, finding this was *a lot* of fun...

opm/core/props/pvt/PvtLiveGas.cpp

@@ -574,12 +574,6 @@ namespace Opm
                                                  press);
             } else {  // Undersaturated case
                 int is = tableIndex(saturatedGasTable[0], press);
-                // Extrapolate from first table section
-                if (is == 0 && press < saturatedGasTable[0][0]) {
-                    return linearInterpolation(undersatGasTables[0][0],
-                                                     undersatGasTables[0][item],
-                                                     r);
-                }
 
                 // Extrapolate from last table section
                 //int ltp = saturatedGasTable[0].size() - 1;