update default.xml.

Init refs/tags/OpenHarmony-v3.1-Beta tags
Signed-off-by: Nmamingshuai <mamingshuai1@huawei.com>

default.xml

@@ -2,7 +2,7 @@
 <manifest>
   <remote fetch="." name="origin" review="https://openharmony.gitee.com/openharmony/"/>
   <remote fetch="https://gitee.com/openharmony-sig" name="sig" review="https://gitee.com/openharmony-sig/"/>
-  <default remote="origin" revision="OpenHarmony-3.1-Beta" sync-j="4" />
+  <default remote="origin" revision="refs/tags/OpenHarmony-v3.1-Beta" sync-j="4" />
 
   <project name="miscservices_inputmethod" path="base/miscservices/inputmethod" />