Remove outdated/obsolete README

The README for the API reference top-level is completely obsolete, so we
should just remove it.

https://bugzilla.gnome.org/show_bug.cgi?id=790896

docs/reference/README

@@ -1,63 +0,0 @@
-This package contains the reference documentation
-for GLib. For more information about Glib,
-see:
-
- http://www.gtk.org
-
-For information about contributing to the
-GLib/GTK+ reference documentation project, see:
-
- http://www.gtk.org/rdp/
-
-The GLib reference documentation is freely redistributable,
-see the file COPYING for details.
-
-
-REQUIREMENTS
-============
-
-To build the documentation, you must have the gtk-doc
-package installed. To rebuild the template files,
-you must have the current version of the GLib
-header files installed.
-
-
-BUILD
-=====
-
-First, run configure to generate the makefiles for this
-module. There is one option specific to this package
-
-  --with-html-dir=DIR   top of installed HTML documentation tree
-
-
-The Makefiles for this module define three targets:
-
- templates:
-  
-  Scan the headers and merge the results with the current 
-  template files
-
- sgml:
-
-  Generate SGML files using the DocBook DTD from
-  the template files
-
- html:
-
-  Generate HTML from the SGML files.
-
-To build the documentation, do:
-
- make sgml
- make html
-
-You should only run the 'make templates' step if you
-need to regenerate the templates for a more recent
-version of the GLib sources.
-
-
-INSTALLATION
-============
-
- make install