Remove the findPhreaticSurface function

[MostafaGomaa93]

I was testing the code with variable groundwater depth through time (the main purpose was to track issue 242 for the groundwater temperature) and by coincidence I found out that the function findPhreaticSurface is not working correctly with variable groundwater depth. This function should find the soil layer that includes the phreatic surface (saturated zone) and is used in the groundwater recharge calculations. It is adopted from the FINDTABLE in STEMMUS_MODFLOW. However, the test with variable groundwater depth shows a shift between the indxGWLay and the indxBotmLayer_R (the check in this line) and that shift is expanding through the time (definitions of indxGWLay and the indxBotmLayer_R are here).

I add couple of lines in the calculateGroundwaterRecharge that does similar to the findPhreaticSurface function, but shorter and works correctly with the case of variable groundwater depth.