Screens broadcast a news conference by U.S. Federal Reserve Chair Jerome Powell, on the floor of the New York Stock Exchange last October. | REUTERS A decision by U.S. District Attorney Jeanine Pirro to drop a criminal probe into the Federal Reserve potentially clears a path for President Donald Trump’s nominee to take over the central bank. What it won’t do is secure the current Fed chair’s departure. Jerome Powell has pledged to remain at the U.S. central bank until the Department of Justice probe, related to cost overruns in a building renovation, is completed "with transparency and finality.” It’s not clear that Pirro’s move, which defers the investigation to the Fed’s own Office of Inspector General, will meet that test.…