It's not quite a lump of coal in their stockings this Christmas season, but for Goldman Sachs' top  executives, it's the next worst thing -- no cash bonuses this year.  Goldman says that, instead of cash, its 30 high-ranking executives will receive stock that cannot be sold for at least five years, as the Wall Street giant bows to criticism over its pay practices.  But the measures will not affect Goldman's other 31,000 employees, including top traders who are likely to be handsomely rewarded for helping Goldman Sachs turn profits this year.   Politicians have chastised Wall Street bankers for taking excessive risk, which resulted in big bonuses but also helped lead to the credit crisis and recession.