Unnecessary array assignment in hydro optimization management

[nikolaredstork]

In mothly hydro management, when reservoir management is not used, monthly optimal levels array is populated with average reservoir levels. Don't see purpose of assigning monthly optimal level array when reservoir management is not used, in this case there is no reservoir to be filled with inflows and we don't need any arrays that represents reservoir levels. In src/solver/hydro/management/montlhy.cpp file, you can find that one line of code that I found unnecessary, function is called prepareMonthlyOptimalGenerations.