[TableGen] Use `std::move` to avoid copy (#123088)

diff --git a/llvm/utils/TableGen/DecoderEmitter.cpp b/llvm/utils/TableGen/DecoderEmitter.cpp
index 90a6d0e..3f79de3 100644
--- a/llvm/utils/TableGen/DecoderEmitter.cpp
+++ b/llvm/utils/TableGen/DecoderEmitter.cpp
@@ -2146,7 +2146,7 @@
         InsnOperands.push_back(std::move(OpInfo));
     }
   }
-  Operands[Opc] = InsnOperands;
+  Operands[Opc] = std::move(InsnOperands);
 
 #if 0
   LLVM_DEBUG({