External reference to non-existing "features" manual in grub documentation.

[Andrey Borzenkov]

grub.texi contains

The list of commands (@pxref{Commands}) are a subset of those supported
for configuration files. Editing commands closely resembles the Bash
command-line (@pxref{Command Line Editing, Bash, Command Line Editing,
features, Bash Features})

Where document "features" comes from? Is it expected to be part of Bash
documentation or was planned to be written as part of grub
documentation set?