_s: Revert f955fca630

The leading whitespace is needed to replace this `_s` instance with the theme name.
It's obviously a hack, since it also leaves the theme name with a leading white space, but short of adding a new replace logic for this specific line in `style.css`, it's the easiest way to achieve that.

See #304, where this was brought up before.
Merge remote-tracking branch 'upstream/master' into ja

* upstream/master:
  _s: Revert f955fca630