Delete gke-usage.yaml

The plugin is unmaintained, its repository is archived

https://github.com/BESTSELLER/backstage-plugin-gkeusage/issues/255#issuecomment-1240335020

Signed-off-by: David Jetelina <6594163+djetelina@users.noreply.github.com>

microsite/data/plugins/gke-usage.yaml

@@ -1,15 +0,0 @@
----
-title: GKE Usage
-author: BESTSELLER
-authorUrl: https://bestsellerit.com
-category: Discovery
-description: This plugin will show you the cost and resource usage of your application within Google Kubernetes Engine (GKE).
-documentation: https://github.com/BESTSELLER/backstage-plugin-gkeusage/blob/master/README.md
-iconUrl: img/gke-logo.png
-npmPackageName: '@bestsellerit/backstage-plugin-gkeusage'
-tags:
-  - gke
-  - cost
-  - google
-  - usage
-  - metering