!504 update repo command for 2.2 beta2

Merge pull request !504 from duangavin123/master

zh-cn/release-notes/OpenHarmony-v2.2-beta2.md

@@ -68,7 +68,7 @@
 通过repo + ssh 下载（需注册公钥，请参考[码云帮助中心](https://gitee.com/help/articles/4191)）。
 
 ```
-repo init -u git@gitee.com:openharmony/manifest.git -b OpenHarmony-2.2-Beta2 --no-repo-verify
+repo init -u git@gitee.com:openharmony/manifest.git -b refs/tags/OpenHarmony-v2.2-Beta2 --no-repo-verify
 repo sync -c
 repo forall -c 'git lfs pull'
 ```
@@ -78,7 +78,7 @@ repo forall -c 'git lfs pull'
 通过repo + https 下载。
 
 ```
-repo init -u https://gitee.com/openharmony/manifest.git -b OpenHarmony-2.2-Beta2 --no-repo-verify
+repo init -u https://gitee.com/openharmony/manifest.git -b refs/tags/OpenHarmony-v2.2-Beta2 --no-repo-verify
 repo sync -c
 repo forall -c 'git lfs pull'
 ```