Documentation: kernel-docs: Remove entry for vfs.txt

It's unnecessary to point to an external mirror of the Documentation
directory.

Jonathan Corbet writes in favor of removing this entry, instead of
moving it under "Docs at the Linux Kernel tree":

> We don't want to turn kernel-docs.rst into yet another out-of-date
> index for the rest of Documentation/, and the removal of the external
> URL takes away the only bit of additional information that this entry
> offers.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/kernel-docs.rst

@@ -95,18 +95,6 @@ On-line docs
         [...]. This paper examines some common problems for
         submitting larger changes and some strategies to avoid problems.
 
-    * Title: **Overview of the Virtual File System**
-
-      :Author: Richard Gooch.
-      :URL: http://www.mjmwired.net/kernel/Documentation/filesystems/vfs.txt
-      :Date: 2007
-      :Keywords: VFS, File System, mounting filesystems, opening files,
-        dentries, dcache.
-      :Description: Brief introduction to the Linux Virtual File System.
-        What is it, how it works, operations taken when opening a file or
-        mounting a file system and description of important data
-        structures explaining the purpose of each of their entries.
-
     * Title: **Linux Device Drivers, Third Edition**
 
       :Author: Jonathan Corbet, Alessandro Rubini, Greg Kroah-Hartman