[VPlan] Remove duplicated computeCost call (NFC).

Remove a redundant duplicated computeCost call. NFC, just skipping an
unneeded call.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -280,7 +280,6 @@ InstructionCost VPRecipeBase::cost(ElementCount VF, VPCostContext &Ctx) {
   if (UI && Ctx.skipCostComputation(UI, VF.isVector())) {
     RecipeCost = 0;
   } else {
-    RecipeCost = computeCost(VF, Ctx);
     RecipeCost = computeCost(VF, Ctx);
     if (ForceTargetInstructionCost.getNumOccurrences() > 0 &&
         RecipeCost.isValid()) {