Fixes documentation of external-path tag

As for the implementation the paths tag "external-path" points to
the path returned by Environtments.getExternalStorageDirectory()
The documentation, however, reported otherwise.

This was also reported here:
https://code.google.com/p/android/issues/detail?id=61170

Change-Id: Ic58003bafab479501c5b7e83132877906e3cc822
(cherry picked from commit cdb0be0e10a15e039b216879b2e1931c7515d340)
1 file changed