[pylint] Pylint 2.10 - fix redundant-u-string-prefix

Pylint 2.10 added new default checks [1]:

redundant-u-string-prefix:
  Emitted when the u prefix is added to a string

[1] https://pylint.pycqa.org/en/latest/whatsnew/2.10.html
[2] https://github.com/PyCQA/pylint/issues/4102



Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>