Remove dead forward decl

Author: lukel97

llvm/include/llvm/Analysis/LoopAnalysisManager.h

@@ -37,7 +37,6 @@ namespace llvm {
 class AAResults;
 class AssumptionCache;
 class BlockFrequencyInfo;
-class BranchProbabilityInfo;
 class DominatorTree;
 class Function;
 class Loop;