Synchronizing Vector jQuery UI styling with core to fix regression

Applying fix from change Ib3e0fc57 to Vector's jQuery UI styling as
it should have been fixed in both places. The on-wiki fix was removed
prematurely, as the bug was only fixed for non-Vector skins.

This fixes bad formatting of audio player on Wikipedia (see bug).

Bug: 71601
Change-Id: I80bef309dca9ea551134341037f6d96ad0f5c7e7