[LyX/master] Update Russian localization

[Juergen Spitzmueller]

commit 1af9e3b0fc096e464c20c7cdd48145c335a50086
Author: Yuriy Skalko <yuriy.skalko at gmail.com>
Date:   Fri Aug 7 20:26:37 2020 +0300

    Update Russian localization

 lib/doc/ru/Math.lyx                            |   85 +++++++------
 lib/doc/ru/Tutorial.lyx                        |   13 +-
 lib/doc/ru/UserGuide.lyx                       |  163 ++++++++++++++----------
 lib/examples/ru/Graphics_and_Insets/XY-Pic.lyx |  101 +++++++++------
 po/ru.po                                       |  145 +++++++++++-----------
 5 files changed, 284 insertions(+), 223 deletions(-)