Documentation: update example conf for "mirror all branches"

Doc is suggesting <repo>:* to mirror all manifest branches, but
in the code we require <repo>:refs/heads/*.

Update documentation so example and text use the refs/heads/*

Change-Id: Iacd78ec9bc92c59a17e39e03638b9f5920f577d3
diff --git a/java/Documentation/about.md b/java/Documentation/about.md
index 2d5e0f7..54a5d34 100644
--- a/java/Documentation/about.md
+++ b/java/Documentation/about.md
@@ -48,14 +48,14 @@
    Setting it true will cause repos that are not accessible to be ignored.
 
 
-For the destination branch, you may also specify `*` to copy all branches in the
-manifest repository. In this case the `srcRef` field is not required (it will be
-ignored if present). Specific branches can be excluded with the `exclude`
-option. `exclude` value is a comma-separated list of fully qualified refs
-(i.e. with the `refs/heads/` prefix).
+For the destination branch, you may also specify `refs/heads/*` to copy all
+branches in the manifest repository. In this case the `srcRef` field is not
+required (it will be ignored if present). Specific branches can be excluded with
+the `exclude` option. `exclude` value is a comma-separated list of fully
+qualified refs (i.e. with the `refs/heads/` prefix).
 
 ```
-[superproject "submodules:*"]
+[superproject "submodules:refs/heads/*"]
    srcRepo = platforms/manifest
    srcPath = manifest.xml
    exclude = refs/heads/test,refs/heads/ignoreme