ru: make ь (soft mark) absolutely silent befor iotated vowel

This affect e.g. pronunciation of я (ja) because j then starts from
pause

dictsource/ru_rules

@@ -440,7 +440,7 @@
      _) ы (_    y
 
 .group ь
-        ь (Y    _|
+        ь (Y    // no pronunciation (i.e. silent)
      _) ь (_    m;'jak;I#jzn'Ak
 
 .group э