Remove trailing whitespace from [27982].

git-svn-id: https://develop.svn.wordpress.org/trunk@27984 602fd350-edb4-49c9-b593-d223f7449a82
Widget Customizer: Move `WidgetCustomizer` to `wp.customize.Widgets`. First pass.

see #27690.

git-svn-id: https://develop.svn.wordpress.org/trunk@27985 602fd350-edb4-49c9-b593-d223f7449a82