TODO: remove TODO, handle bugs and feature requests on gitlab

The old TODO items have now been migrated to gitlab [1]. Remove
TODO.rst. Emphasize gitlab issues for bug reports and feature requests
in the documentation.

[1] https://gitlab.freedesktop.org/drm/maintainer-tools/issues

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Status Job ID Name Coverage
  Build
passed #61127
check

00:00:30

 
  Deploy
passed #61128
pages

00:00:16

passed pages:deploy

00:00:01

failed pages:deploy

00:00:00

failed pages:deploy

00:00:00