Steps to replicate the issue (include links if applicable):

• Change the label and description of an entity schema (e.g. https://test.wikidata.org/w/index.php?diff=717585)
• Change the label again (e.g. https://test.wikidata.org/w/index.php?diff=717586)
• Try to undo the first edit (e.g. https://test.wikidata.org/w/index.php?title=EntitySchema:E14&action=edit&undoafter=537489&undo=717585)

What happens?:

The changes to the description cannot be undone, with the following error:

The edit could not be undone because it has been changed.

What should have happened instead?:

It should behave the same way that it does on items, i.e. it should be possible to undo the changes to the description.

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

For items, after following the same steps, the undo page says

The edit can partially be undone.
1 change cannot be undone because the value has changed in the meantime.

and then allows undoing the changes to the description (e.g. https://test.wikidata.org/w/index.php?title=Q104869&action=edit&undoafter=266880&undo=717590)