fix(language): remove abbreviations in russian (@Dmskrzh) (monkeytypegame#7682)

The abbreviations "НКВД" (Народный комиссариат внутренних дел (People's
Commissariat for Internal Affairs)) and "НЛО" (Неопознанный летающий
объект (Unidentified flying object)) have been removed from russian_5k,
russian_25k, and russian_50k, as there is a separate
russian_abbreviations for abbreviations.

Author: Dmskrzh

frontend/static/languages/russian_25k.json

@@ -12593,7 +12593,6 @@
     "нищенствовать",
     "нищий",
     "нк",
-    "НЛО",
     "н-не",
     "н-ну",
     "но",

frontend/static/languages/russian_50k.json

@@ -24987,8 +24987,6 @@
     "нищета",
     "нищий",
     "нк",
-    "НКВД",
-    "НЛО",
     "нм",
     "н-не",
     "н-нет",

frontend/static/languages/russian_5k.json

@@ -3935,7 +3935,6 @@
     "обвинение",
     "мэр",
     "школьник",
-    "НКВД",
     "беречь",
     "молиться",
     "рюкзак",