Revert "Update displaytitle on save"

Causing HTTP 500 errors in ApiVisualEditorEdit.php (calling
getDisplayTitle() on a non-object).

This reverts commit dedc89b5ff9bd357bbbdff484361fa6deb128630.

Bug: 66792
Change-Id: Iaf438660f0623dc05f76294ad847b2fc5e25bed6
Merge "Revert "Update displaytitle on save""