[SimpleLoopUnswitch] Remove duplicate include.

Header "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" is currently
included twice. This commit removes the duplicate 'include' line.

Previous commit 693eedb
seems to have mistakenly added the duplicate 'include'.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D112979

Author: JOE1994

llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp

@@ -50,7 +50,6 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/GenericDomTree.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Transforms/Utils/Local.h"