doc: update open source banner in chart readme (#392)

Author: TmNguyen12

charts/newrelic-k8s-metrics-adapter/README.md

@@ -1,4 +1,4 @@
-[![New Relic Experimental header](https://github.com/newrelic/opensource-website/raw/master/src/images/categories/Experimental.png)](https://opensource.newrelic.com/oss-category/#new-relic-experimental)
+<a href="https://opensource.newrelic.com/oss-category/#community-plus"><picture><source media="(prefers-color-scheme: dark)" srcset="https://github.com/newrelic/opensource-website/raw/main/src/images/categories/dark/Community_Plus.png"><source media="(prefers-color-scheme: light)" srcset="https://github.com/newrelic/opensource-website/raw/main/src/images/categories/Community_Plus.png"><img alt="New Relic Open Source community plus project banner." src="https://github.com/newrelic/opensource-website/raw/main/src/images/categories/Community_Plus.png"></picture></a>
 
 # newrelic-k8s-metrics-adapter