modify 3.1 releasenotes and the links to this topic

Signed-off-by: NRayShih <shirui721@huawei.com>

README_zh.md

@@ -18,7 +18,7 @@
 
 master：最新开发版本。  
 
-发布OpenHarmony 3.1 Beta版本，[了解版本详情](zh-cn/release-notes/OpenHarmony-v3.1-beta.md)。
+发布OpenHarmony 3.1 Release版本，[了解版本详情](zh-cn/release-notes/OpenHarmony-v3.1-release.md)。
 
 发布OpenHarmony 3.0 LTS版本，[了解版本详情](zh-cn/release-notes/OpenHarmony-v3.0-LTS.md)。该版本已更新至OpenHarmony 3.0.2 LTS，[了解版本详情](zh-cn/release-notes/OpenHarmony-v3.0.2-LTS.md)。
 

zh-cn/release-notes/Readme.md

 # OpenHarmony Release Notes
 ## OpenHarmony 3.x Releases
+-   [OpenHarmony v3.1 Release (2022-03-30)](OpenHarmony-v3.1-release.md)
 -   [OpenHarmony v3.1 Beta (2021-12-31)](OpenHarmony-v3.1-beta.md)
 -   [OpenHarmony v3.0.2 LTS (2022-03-18)](OpenHarmony-v3.0.2-LTS.md)
 -   [OpenHarmony v3.0.1 LTS (2022-01-12)](OpenHarmony-v3.0.1-LTS.md)