update the version json file for website (#7868)

Signed-off-by: Nxiaolong.ran <rxl@apache.org>


### Modifications

Use the 2.6.1 version of the docs as the latest stable version

site2/website/versions.json

 [
-  "2.6.0",
   "2.6.1",
+  "2.6.0",
   "2.5.2",
   "2.5.1",
   "2.5.0",