Revert "Fix unused variable in CoroFrame.cpp when building Release with GCC 10"

This reverts commit ff5e896.

Author: lxfind

llvm/lib/Transforms/Coroutines/CoroFrame.cpp

@@ -1549,7 +1549,6 @@ static void rewritePHIs(BasicBlock &BB) {
     for (BasicBlock *Pred : Preds) {
       if (CatchSwitchInst *CS =
               dyn_cast<CatchSwitchInst>(Pred->getTerminator())) {
-        (void)CS;
         // CleanupPad with a CatchSwitch predecessor: therefore this is an
         // unwind destination that needs to be handle specially.
         assert(CS->getUnwindDest() == &BB);