Update Russian(ru) plural rules to CLDR 24

Russian (ru) plural rules have a major change. The 'few' form is
merged with the 'other' form. The current forms are 'one', 'many', 'other'.
In MW ru plural rules were overridden using convertPlural methdod
in LanguagesRu.php with 3 forms.

Effectively forms[1] and forms[2] are swapped.

Followup: I9930b290d004667a3bb09e5c1663ec2c9c27d8a6

Bug: 56931
Change-Id: Ia5779e42315d3f41f52dce2bfffaee0a4297d23b