package/python-colorzero: bump version to 2.0

package/python-colorzero: bump version to 2.0

- change to python3 only

- update license file hash:
  @@ -1,4 +1,4 @@
  -Copyright 2016-2018 Dave Jones <dave@waveform.org.uk>
  +SPDX-License-Identifier: BSD-3-Clause

Changelog ([1]):

  - Dropped Python 2.x support. Current Python support level is 3.5 and above.

  - Added html and css format specifications to the :class:`Color` class'
    string-formatting capabilities.

[1] https://github.com/waveform80/colorzero/blob/master/docs/changelog.rst

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>