Update CODEOWNERS

Remove several maintainers for object_detection and lstm_object_detection

CODEOWNERS

 * @tensorflow/tf-garden-team @tensorflow/tf-model-garden-team
 /official/ @rachellj218 @saberkun @jaeyounkim
-/official/nlp @saberkun @chenGitHuber @lehougoogle @rachellj218
-/official/vision @pengchongjin @xianzhidu @yeqingli @arashwan @saberkun @rachellj218
+/official/nlp/ @saberkun @chenGitHuber @lehougoogle @rachellj218
+/official/vision/ @pengchongjin @xianzhidu @yeqingli @arashwan @saberkun @rachellj218
 /research/adv_imagenet_models/ @alexeykurakin
 /research/adversarial_crypto/ @dave-andersen
 /research/adversarial_logit_pairing/ @alexeykurakin
@@ -33,14 +33,14 @@
 /research/lfads/ @jazcollins @sussillo
 /research/lm_1b/ @oriolvinyals @panyx0718
 /research/lm_commonsense/ @thtrieu
-/research/lstm_object_detection/ @dreamdragon @masonliuw @yinxiaoli @yongzhe2160
+/research/lstm_object_detection/ @yinxiaoli @yongzhe2160
 /research/marco/ @vincentvanhoucke
 /research/maskgan/ @liamb315 @a-dai
 /research/namignizer/ @knathanieltucker
 /research/neural_gpu/ @lukaszkaiser
 /research/neural_programmer/ @arvind2505
 /research/next_frame_prediction/ @panyx0718
-/research/object_detection/ @jch1 @tombstone @ronnyvotel @derekjchow @jesu9 @dreamdragon @afathi3 @pkulzc
+/research/object_detection/ @jch1 @tombstone @pkulzc
 /research/pcl_rl/ @ofirnachum
 /research/ptn/ @xcyan @arkanath @hellojas @honglaklee
 /research/qa_kg/ @yuyuz