Fewer contenders means fewer constraints on expanding market share.On the frontier of some of biopharma's lucrative markets, one competitor's stumble can be a win for one of its rivals. And it looks like Johnson & Johnson (JNJ 0.38%) just hit a bump in the road that'll pave the way for Eli Lilly (LLY 0.33%) to be more dominant in one such market within neuroscience.Here's what happened, and why it's bullish for Lilly's stock.This growing market now has one less aspiring entrantAs expected, Johnson & Johnson ...