gplugin/gplugin

gi-docgen now errors if your annotations are wrong, so this fixes ours

Testing Done:
Ran the build with docs enabled until it succeeded.

Reviewed at https://reviews.imfreedom.org/r/1131/
// SPDX-FileCopyrightText: 2021 GNOME Foundation
// SPDX-License-Identifier: LGPL-2.1-or-later
// A map between namespaces and base URLs for their online documentation
baseURLs = [
[ 'GLib', 'https://docs.gtk.org/glib/' ],
[ 'GObject', 'https://docs.gtk.org/gobject/' ],
[ 'GModule', 'https://docs.gtk.org/gmodule/' ],
]