MDL-38907 removed the 'Jump to' menu centering that is used by MDL-34917, but did not remove the code:

$select->class = 'jumpmenu';

in '/course/format/renderer.php' that uses it.

Aesthetically I think the text should be center aligned on the menu to bring symmetry with the left and right navigation facility and the css class be put back. Or if that is not desired, the redundant code removed. Or if this considered a theme style issue, that the base theme defines it such that core and contributed themes can choose to override it.