Delete the detection_output_op, which had been split into several operators. (#9121)

Author: qingqing01

paddle/fluid/operators/CMakeLists.txt

@@ -165,7 +165,6 @@ op_library(cond_op DEPS framework_proto tensor net_op)
 op_library(cross_entropy_op DEPS cross_entropy)
 op_library(softmax_with_cross_entropy_op DEPS cross_entropy softmax)
 op_library(softmax_op DEPS softmax)
-op_library(detection_output_op DEPS softmax)
 op_library(sequence_softmax_op DEPS softmax)
 op_library(sum_op DEPS selected_rows_functor)
 op_library(sgd_op DEPS selected_rows_functor)