Merge #6804

6804: Update russian.txt r=def- a=gerdoe-jr

`Наблюдать` -> `Наблюдение за`
`*новых упоминаний` -> `*упоминаний`

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## Checklist

- [ ] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test (especially base/) or added coverage to integration test
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: Vlad <gerdoexx@gmail.com>

data/languages/russian.txt

@@ -403,7 +403,7 @@ Sound error
 == Ошибка звука
 
 Spectate
-== Наблюдать
+== Наблюдение за
 
 Spectate next
 == Наблюдать за след.
@@ -1012,13 +1012,13 @@ Grabs
 == Захватов
 
 1 new mention
-== 1 новое упоминание
+== 1 упоминание
 
 %d new mentions
-== %d новых упоминаний
+== %d упоминаний
 
 9+ new mentions
-== 9+ новых упоминаний
+== 9+ упоминаний
 
 Client message
 == Клиентское сообщение