_s: List post formats in their own line.

d8a88d20976cb388219bb5e52a38232278c8a7f1 brought the HTML5 support declaration close to how Twenty Thirteen and Twenty Fourteen do it, leaving post formats doing their own thing.

Let's make displaying array values consistent with the latest default themes.
Merge remote-tracking branch 'upstream/master' into ja

* upstream/master:
  _s: List post formats in their own line.