AUGUSTA, Maine — Better-than-expected Maine tax revenue numbers led a state panel to lower its key budget shortfall projection by hundreds of millions of dollars this week, but the situation is still dire as lawmakers prepare to negotiate a new spending roadmap.Revenue has outperformed dire projections from earlier in the coronavirus pandemic, though the trajectory of the virus and the scope of any new federal aid package could change Maine’s budget picture in the coming months and determine the depth of spending cuts or new sources of funding policymakers will turn to when they come back to Augusta in early 2021. The Maine Revenue Forecasting Committee revised its revenue predictions upward by $764 million this week after issuing a dismal July projection of a staggering $1.4 billion shortfall over three budget years.