Adds activerecord.errors.models.user_mute.{attributes.subject.format, is_already_muted} under ignore_unused (in i18n-tasks.yml) so they are not reported as unused anymore.
Added time.formats.{blog, friendly} translation keys under ignore_unused in i18n-tasks.yml since used on numerous places for formatting dates / times, removed site.sidebar.close because started being used at 3a51160 and ended being used at 6adcce4, removed sessions.new.title because started being used at f18baae and has been used only in test/system/issues_test.rb (from which we removed it because tests are always in EN)
Removed user_blocks.show.{confirm, needs_view, show} translation keys added at daa2496. confirm and show has never been used, needs_view ended being used at ca06b3c.
Removed users.new.tou (added 9649b19 and has never been used), users.terms.decline replaced with users.terms.cancel and together with users.terms.continue started being used at /users/terms.html.erb (both were added at 9a9e13a and removed at 1be8d59)
Removed unused translation keys changesets.{changeset.anonymous, no_such_entry.title} from en.yml. .anonymous was added in fddda4e and was stopped being used in 3e305fb. .title was added in f0764d3 but never used.
Namefinder was introduced in commit d2bd786 and later removed in fcebfd1f. Since then, these translation strings are unused.
Analysis using: `git log -p -S "towns" -- ':(exclude)*config/locales/*.yml' ':(exclude)*vendor/assets/*'`
Translation keys are used for OmniAuth callbacks, and defined by the
respective OmniAuth provider. It is expected that these strings are
unsued in the OSM website repo.
Removed unused translations activerecord.errors.messages.{invalid_email_address, email_address_not_routable} started / ended using in 63862d0 / 90a7efc.
Removed keys traces.make_public.made_public (started / ended using in 95595ee / 5651714) and traces.trace_optionals.tags (started / ended using in c30f141 / 7410b59).
