fix(i18n): make future-tense block time text translatable

fix(i18n): make future-tense block time text translatable

block_short_time_in_future rendered its relative-duration text via
time_ago_in_words with no :scope, falling back to Rails' bundled
gem-default locale data instead of the app's own translatable
config/locales files (issue #5769). Mirror the existing
distance_in_words_ago pattern used by block_short_time_in_past: add a
symmetric distance_in_words_in scope and point the helper at it, and
drop the hardcoded literal "in " from time_in_future_title so the
direction word is fully translator-controlled, like the past-tense
string already is.