Fix broken chart icon links #1289 (#1290)

Signed-off-by: junya koyama <arukiidou@yahoo.co.jp>

Author: arukiidou

deploy/helm-chart/Chart.yaml

@@ -5,7 +5,7 @@ type: application
 version: 1.0.0
 appVersion: "edge"
 home: https://github.com/nginxinc/nginx-gateway-fabric
-icon: https://raw.githubusercontent.com/nginxinc/nginx-gateway-fabric/tree/main/deploy/helm-chart/chart-icon.png
+icon: https://raw.githubusercontent.com/nginxinc/nginx-gateway-fabric/main/deploy/helm-chart/chart-icon.png
 sources:
   - https://github.com/nginxinc/nginx-gateway-fabric/tree/main/deploy/helm-chart
 keywords: