Fix positioning error with draggable, revert and grid

Fix positioning error with draggable, revert and grid

This minor change fixes an error when using draggable revert and grid.

Since upgrading of jQuery UI probably won't happen in the near future [1]
I looked for another way to fix the issue.

See [2]. Unlike stated in the second comment adding the lines below
won't fix the bug. Moving the lines up fixed the issue.

See also the description of the bug in [3].

[1] https://phabricator.wikimedia.org/T71386
[2] https://bugs.jqueryui.com/ticket/4696
[3] https://phabricator.wikimedia.org/T140965#2944610

Bug: T140965
Change-Id: Ib0f386c6a2447740f44591be70c34cf4a83b88c4