Update copyright notices.

Author: KelSolaar

CONTRIBUTORS.rst

@@ -12,6 +12,6 @@ About
 -----
 
 | **Colour - Dash** by Colour Developers
-| Copyright © 2018-2021 – Colour Developers – `colour-developers@colour-science.org <colour-developers@colour-science.org>`__
+| Copyright 2018 – Colour Developers – `colour-developers@colour-science.org <colour-developers@colour-science.org>`__
 | This software is released under terms of New BSD License: https://opensource.org/licenses/BSD-3-Clause
 | `https://github.com/colour-science/colour-dash <https://github.com/colour-science/colour-dash>`__

README.rst

@@ -59,6 +59,6 @@ About
 -----
 
 | **Colour - Dash** by Colour Developers
-| Copyright © 2018-2021 – Colour Developers – `colour-developers@colour-science.org <colour-developers@colour-science.org>`__
+| Copyright 2018 – Colour Developers – `colour-developers@colour-science.org <colour-developers@colour-science.org>`__
 | This software is released under terms of New BSD License: https://opensource.org/licenses/BSD-3-Clause
 | `https://github.com/colour-science/colour-dash <https://github.com/colour-science/colour-dash>`__