chore(docs): Remove -icon string from icon png's (#2040)

* rename icons (remove `-icon`)

* Remove (`-icon`) from chart.yaml

* Add 2 icons

* slight format change

* remove -icon

charts/stable/nextcloud/Chart.yaml

@@ -16,7 +16,7 @@ deprecated: false
 description: A private cloud server that puts the control and security of your own
   data back into your hands.
 home: https://nextcloud.com/
-icon: https://truecharts.org/_static/img/appicons/nextcloud-icon.png
+icon: https://truecharts.org/_static/img/appicons/nextcloud.png
 keywords:
 - nextcloud
 - storage