Remove aggregation dependency from project files

Change-Id: Idfd3941f47b71d6b84306d88604b744e3585e4af
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/diffeditor/diffeditor.qbs

@@ -4,7 +4,6 @@ QtcPlugin {
     name: "DiffEditor"
 
     Depends { name: "Qt.widgets" }
-    Depends { name: "Aggregation" }
     Depends { name: "Utils" }
 
     Depends { name: "Core" }