Do not reset item weight while removing an item

Problem/Motivation

Guess the following scenario: a user uploads a new media item to a a field (cardinality set to unlimited). Then the users reorders the media items (i.e. move the new item to the top of the list).
Before saving, the user decides to remove one of the other items.

Result: the item is removed and the original item order is restored (having the new item at the bottom of the list).

Proposed resolution

Change the behaviour, so the item order is retained after removing an item.

Remaining tasks

Create patch.