devel/py-spyder-kernels: Update to 2.1.3

Fix errors when setting or getting the Matplotlib backend.

Changelog: https://github.com/spyder-ide/spyder-kernels/blob/master/CHANGELOG.md#version-213-2021-10-02

Reported by: Repology
MFH: 2021Q4

(cherry picked from commit f3a1b59d79681f95bbb7fe24aa9448886b764f61)