[LyX/master] Update Russian localization

[Juergen Spitzmueller]

commit ace9fbb6a087354e3ccbf9f33eb83a54d247eb65
Author: Yuriy Skalko <yuriy.skalko at gmail.com>
Date:   Fri Sep 4 19:03:15 2020 +0300

    Update Russian localization

 lib/doc/ru/Math.lyx         |   10 +-
 lib/doc/ru/UserGuide.lyx    |  564 +++++++++++++++++++++----------------------
 lib/examples/ru/Welcome.lyx |    2 +-
 po/ru.po                    |  244 ++++++++++----------
 4 files changed, 403 insertions(+), 417 deletions(-)