Remove "cpp-v8-extra" string from locales

As the choice itself was pruned in 0aa78e7 (see gh-129),
  logical thing is to get rid of its translations too.

Signed-off-by: Aleksandrs Ļedovskis <aleksandrs@ledovskis.lv>
Merge pull request #132 from aledovsky/chore/remove_v8monkey_strings

Remove "cpp-v8-extra" string from locales