doxygen: Update .gitignore

doxygen: Update .gitignore

The last of these output directories was removed in 2007.

  commit c2e0570831ae130fce1fa374bebe25bb9c561e29
  Author: Jerome Glisse <glisse@freedesktop.org>
  Date:   Fri Feb 16 23:18:56 2007 +0100

      Update doxygen doc to reflet vbo changes.

      Update doxygen doc, array_cache no longuer exist,
      new shiny vbo modules is there. Tested on unix,
      but i think i didn't broke that bat :).

  commit 3ef972f538e1ff207f5919a8068bf14af18fb270
  Author: Brian Paul <brian.paul@tungstengraphics.com>
  Date:   Sun May 16 22:07:02 2004 +0000

      Replaced 'core' with 'main'.
      Other minor updates.

  commit 69db632a9df035cdc852cc64fb14038919929a70
  Author: Jose Fonseca <j_r_fonseca@yahoo.co.uk>
  Date:   Thu May 1 23:32:54 2003 +0000

      Move the Doxygen configuration files into the usual places and integrate with the build system.

Signed-off-by: Rhys Kidd <rhyskidd@gmail.com>
Acked-by: Emil Velikov <emil.velikov@collabora.com>