[LyX/master] Update Russian localization

[Juergen Spitzmueller]

commit d4e9a268e0b8b3cfe3174e605e86d909df239d87
Author: Yuriy Skalko <yuriy.skalko at gmail.com>
Date:   Thu Aug 20 13:55:20 2020 +0300

    Update Russian localization

 lib/doc/ru/Intro.lyx     |   14 +-
 lib/doc/ru/Math.lyx      |   12 +-
 lib/doc/ru/Tutorial.lyx  |   12 +-
 lib/doc/ru/UserGuide.lyx |  826 +++++++++++++++++++++++-----------------------
 po/ru.po                 |  138 ++++----
 5 files changed, 493 insertions(+), 509 deletions(-)