Vim: replace expanded spaces with hard tabs in JS snippet

As suggested by @lencioni here:

  https://github.com/wincent/wincent/commit/ded70d298993ae5cc496a9a

It still expands to two spaces when used (according to the prevailing
settings) and is one byte shorter to boot.

Signed-off-by: Wincent Colaiuta <win@wincent.com>