[LyX/master] Update Russian localization

[Juergen Spitzmueller]

commit 3761058f2c7eae698591c5b7e7e31bbbf318632c
Author: Yuriy Skalko <yuriy.skalko at gmail.com>
Date:   Tue Aug 18 17:10:23 2020 +0300

    Update Russian localization

 lib/doc/ru/Math.lyx      |   14 +-
 lib/doc/ru/Tutorial.lyx  |    6 +-
 lib/doc/ru/UserGuide.lyx |   94 +++++++------
 po/ru.po                 |  337 +++++++++++++++-------------------------------
 4 files changed, 172 insertions(+), 279 deletions(-)