update default.xml.

init OpenHarmony-3.1-Release
Signed-off-by: Nmamingshuai <mamingshuai1@huawei.com>

default.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <manifest>
   <remote fetch="." name="origin" review="https://openharmony.gitee.com/openharmony/"/>
-  <default remote="origin" revision="weekly_20220301" sync-j="4" />
+  <default remote="origin" revision="OpenHarmony-3.1-Release" sync-j="4" />
 
   <project name="miscservices_inputmethod" path="base/miscservices/inputmethod" />