Retire maintainers

Yang Feng and Yuanmao Zhu has been contributed to the project as
maintainers, and now they are not active due to other issues. So we move
them to retired maintainers.

Thanks for all their contributions!

Signed-off-by: Baohua Yang <yangbaohua@gmail.com>

Author: yeasy

MAINTAINERS.md

@@ -3,16 +3,13 @@
 | Name | GitHub | Email |
 |---|---|---|
 | Baohua Yang | yeasy | yangbaohua@gmail.com |
-| Yang Feng | fengyangsy | fengyang.09186@h3c.com |
-| Yuanmao Zhu | zhuyuanmao | yuanmao@ualberta.ca |
 | Xichen Pan | xichen1 | xichen.pan@gmail.com  |
 | Haibo Yang | YoungHypo | haiboyang@umail.ucsb.edu  |
 
 ## Release Managers
 
 | Name | GitHub | Email |
 |---|---|---|
-| Yang Feng | fengyangsy | fengyang.09186@h3c.com |
 
 ## Retired Maintainers
 
@@ -22,5 +19,7 @@
 | Tong Li | tongli | litong01@us.ibm.com |
 | Haitao Yue | hightall | hightallyht@gmail.com |
 | Qiang Xu | XuHugo | xq-310@163.com |
+| Yang Feng | fengyangsy | fengyang.09186@h3c.com |
+| Yuanmao Zhu | zhuyuanmao | yuanmao@ualberta.ca |
 
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