Revert "[mlir][Presburger] Fix warning Wreturn-std-move (NFC)"

This reverts commit a4070a5.
It introduced another warning instead.

mlir/lib/Analysis/Presburger/PresburgerRelation.cpp

@@ -13,8 +13,6 @@
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SmallBitVector.h"
 
-#include <utility>
-
 using namespace mlir;
 using namespace presburger;
 
@@ -146,7 +144,7 @@ PresburgerRelation PresburgerRelation::computeReprWithOnlyDivLocals() const {
   PresburgerRelation result(getSpace());
   for (const IntegerRelation &disjunct : disjuncts)
     result.unionInPlace(disjunct.computeReprWithOnlyDivLocals());
-  return std::move(result);
+  return result;
 }
 
 /// Return the set difference b \ s.