Kevin Smith's appearance on the Tonight Show, originally scheduled for June 24 (see 'Kevin Smith To Appear On NBC's Tonight Show'), has been moved up one day to Tuesday, June 25.   This time Smith, who in addition to writing and directing films does the popular 'Roadside Attractions' features for the Tonight Show, will be promoting his five-issue Spider-Man/Black Cat mini-series.  The first issue of Smith's new series for Marvel Comics hits stores Wednesday, so the timing is perfect.