Licence claryfication

[kloczek]

In

mpl-sphinx-theme/setup.py

Line 10 in 2b27ba9

license="BSD",

as licence is used BSD.
Because in

mpl-sphinx-theme/mpl_sphinx_theme/_version.py

Lines 4 to 5 in 2b27ba9

	# Copyright (c) Matplotlib developers.
	# Distributed under the terms of the Modified BSD License.

I'm assuming that it is BSD-3-Clause (https://opensource.org/licenses/BSD-3-Clause/).
However in https://github.com/matplotlib/mpl-sphinx-theme/blob/main/LICENSE.txt is completely different Licence.