Updating Russian pages to match English pages

[artemkorsakov]

Updating Russian pages to match English pages:

Changes from:

• https://github.com/scala/docs.scala-lang/pull/2930
• https://github.com/scala/docs.scala-lang/pull/2931
• https://github.com/scala/docs.scala-lang/pull/2934
• https://github.com/scala/docs.scala-lang/pull/2949
• https://github.com/scala/docs.scala-lang/pull/2956
• https://github.com/scala/docs.scala-lang/pull/2981

[artemkorsakov]

@DespiteDeath @kotobotov @evgeny-rybnikov please, review this PR

[artemkorsakov]

@bishabosha @sjrd please, merge this approved PR