Depending on the amount of meta boxes and the layout settings under Screen Options, sortable meta boxes may not be actually sortable.
In these cases, jQuery UI sortable needs to be disabled and the user interface shouldn't use a CSS `cursor: move`.
The use of consistent and relevant cursors may be important for users who have a cognitive disability, since cursors give a visual clue as to an element's functionality. Using the move cursor for elements which cannot be moved may be confusing or counter-intuitive for users.
Props adamsilverstein, antpb, anevins.
Fixes#47131.
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