Update GitHub workflow badge

Author: szkiba

README.md

@@ -1,5 +1,5 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/grafana/xk6-dashboard)](https://goreportcard.com/report/github.com/grafana/xk6-dashboard)
-[![GitHub Actions](https://github.com/grafana/xk6-dashboard/workflows/Test/badge.svg)](https://github.com/grafana/xk6-dashboard/actions?query=workflow%3ATest+branch%3Amaster)
+[![GitHub Actions](https://github.com/grafana/xk6-dashboard/actions/workflows/validate.yml/badge.svg)](https://github.com/grafana/xk6-dashboard/actions/workflows/validate.yml)
 [![codecov](https://codecov.io/gh/grafana/xk6-dashboard/graph/badge.svg?token=ORDNEEZIV3)](https://codecov.io/gh/grafana/xk6-dashboard)
 ![GitHub Downloads](https://img.shields.io/github/downloads/grafana/xk6-dashboard/total)
 [![GitHub Release](https://img.shields.io/github/v/release/grafana/xk6-dashboard)](https://github.com/grafana/xk6-dashboard/releases/)