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/incubator/piwigo/Chart.yaml

@@ -7,7 +7,7 @@ dependencies:
 description: A is photo gallery software for the web, built by an active community
   of users and developers.
 home: https://github.com/truecharts/apps/tree/master/charts/stable/piwigo
-icon: https://truecharts.org/_static/img/appicons/piwigo-icon.png
+icon: https://truecharts.org/_static/img/appicons/piwigo.png
 keywords:
 - piwigo
 - gallery