[NFC][CostModel][ARM] Remove redundant lambda capture

Buildbot failures were caused by PR llvm#122713. This
was due to unused captures in a lambda function.

Change-Id: Ie0907396c2551190dd982bfa180934b4075271d8

Author: nasherm

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

@@ -1486,7 +1486,7 @@ InstructionCost ARMTTIImpl::getArithmeticInstrCost(
     auto IsExtInst = [](const Value *V) -> bool {
       return isa<ZExtInst>(V) || isa<SExtInst>(V);
     };
-    auto IsExtensionFromHalf = [&, IsExtInst](const Value *V) -> bool {
+    auto IsExtensionFromHalf = [](const Value *V) -> bool {
       return cast<Instruction>(V)->getOperand(0)->getType()->isIntegerTy(16);
     };