[devhelp/docgen: 2/3] Drop gtk-doc files

[Emmanuele Bassi <ebassi src gnome org>]

commit 804ad7b6978ed2d7293e486c93b90780693f877e
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Jul 15 14:43:03 2021 +0100

    Drop gtk-doc files
    
    We use gi-docgen for our API reference, now.

 docs/reference/api-breaks.xml            | 305 ----------------------
 docs/reference/devhelp-docs.xml          | 112 ---------
 docs/reference/devhelp-sections.txt      | 417 -------------------------------
 docs/reference/xml/gtkdocentities.ent.in |   3 -
 docs/reference/xml/meson.build           |  12 -
 5 files changed, 849 deletions(-)