show nested elements in embedded index for revisions

[i-just]

Description

When viewing revisions, the nested entries weren’t showing for matrix fields with element index view mode.

Replication steps:

• create a matrix field with view mode: element index
• create an entry type with that matrix field
• create a section with that entry type and have revisions on
• create an entry in that section, add 2 entries to the matrix field and save
• remove one of the nested entries from the matrix field and save
• view the first revision - both nested entries should show in the matrix field, but without this change, none were showing

Related issues

[brandonkelly]

Thanks!