[CanonicalizeBorrowScope] Removed spurious call.

When canonicalizing an argument, liveness is not used (it being the full
body of the function), so there's no need to invalidate it.

Author: nate-chandler

lib/SILOptimizer/Utils/CanonicalizeBorrowScope.cpp

@@ -824,8 +824,6 @@ bool CanonicalizeBorrowScope::canonicalizeFunctionArgument(
 
   LLVM_DEBUG(llvm::dbgs() << "*** Canonicalize Borrow: " << borrowedValue);
 
-  SWIFT_DEFER { liveness.invalidate(); };
-
   RewriteInnerBorrowUses innerRewriter(*this);
   beginVisitBorrowScopeUses(); // reset the def/use worklist