Fix english doc api, invloves the op of retinanet_target_assign, sigmoid_focal_loss and retinanet_detection_output. (#20250)

* test=document_fix
test=develop
Fix english doc api, invloves the op of retinanet_target_assign, sigmoid_focal_loss and retinanet_detection_output.

* test=document_fix
test=develop
remove Notice: this OP supports CPU mode only in english doc api of retinanet_target_assign and retinanet_detection_output

* test=document_fix
test=develop
fix API Difference for retinanet_target_assign and retinanet_detection_output

* fix API.spec conflicts in english doc api of retinanet_target_assign, sigmoid_focal_loss,  retinanet_detection_output
test=develop
test=document_fix

* fix API.spec conflicts in english doc api of retinanet_target_assign, sigmoid_focal_loss, retinanet_detection_output
test=develop
test=document_fix