[Cherry Pick]Fix bug in sequence_slice_op (#13622)

* Fix bug in sequence_slice_op

test=release/1.0.0

paddle/fluid/operators/sequence_slice_op.h

@@ -75,11 +75,11 @@ class SequenceSliceOpKernel : public framework::OpKernel<T> {
     }
 
     for (size_t i = 0; i < n; ++i) {
-      PADDLE_ENFORCE_LT(0, offset_data[i],
+      PADDLE_ENFORCE_LE(0, offset_data[i],
                         "The offset[%d] must greater than zero.", i);
       PADDLE_ENFORCE_LT(0, length_data[i],
                         "The length[%d] must greater than zero.", i);
-      PADDLE_ENFORCE_LT(lod[0][i] + offset_data[i] + length_data[i],
+      PADDLE_ENFORCE_LE(lod[0][i] + offset_data[i] + length_data[i],
                         lod[0][i + 1], "The target tensor's length overflow.");
     }