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/uptimerobot-prometheus/Chart.yaml

@@ -6,7 +6,7 @@ dependencies:
   version: 9.0.0
 deprecated: false
 description: Prometheus Exporter for the official uptimerobot CLI
-icon: https://truecharts.org/_static/img/appicons/uptimerobot-prometheus-icon.png
+icon: https://truecharts.org/_static/img/appicons/uptimerobot-prometheus.png
 home: https://github.com/k8s-at-home/charts/tree/master/charts/stable/uptimerobot-prometheus
 keywords:
 - uptimerobot