Fix whitespace

Created by: Starsam80

Caused by https://github.com/twbs/bootstrap/commit/e11e6ec9133e8f7eb5c06829233fd12403947e55#diff-cd8ec88dc7823a5c78f7111e37a78adbR29 Also fixes Travis CI and grunt (scss-lint): https://travis-ci.org/twbs/bootstrap/builds