[BOLT][NFC] Remove unused BF::computeLocalUDChain method definition

The function is only used inside AArch64MCPlusBuilder class, there are no uses
of it as a BinaryFunction method.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D126220

bolt/include/bolt/Core/BinaryFunction.h

@@ -667,9 +667,6 @@ private:
                                            uint64_t Offset,
                                            uint64_t &TargetAddress);
 
-  DenseMap<const MCInst *, SmallVector<MCInst *, 4>>
-  computeLocalUDChain(const MCInst *CurInstr);
-
   BinaryFunction &operator=(const BinaryFunction &) = delete;
   BinaryFunction(const BinaryFunction &) = delete;