Update github workflow status (#446)

Author: RewardedIvan

README.md

@@ -4,7 +4,7 @@
 
 ![GitHub all releases](https://img.shields.io/github/downloads/lambda-client/lambda/total?color=seagreen)
 ![CodeFactor grade](https://img.shields.io/codefactor/grade/github/lambda-client/lambda?color=royalblue)
-![GitHub workflow status](https://img.shields.io/github/workflow/status/lambda-client/lambda/gradle_build?logo=gradle)
+![GitHub workflow status](https://img.shields.io/github/actions/workflow/status/lambda-client/lambda/nightly_build.yml?branch=master&logo=gradle)
 [![Discord](https://img.shields.io/discord/834570721070022687?color=skyblue&logo=discord&logoColor=white)](https://discord.gg/QjfBxJzE5x)
 ![GitHub repo size](https://img.shields.io/github/repo-size/lambda-client/lambda)
 ![Lines of code](https://img.shields.io/tokei/lines/github/lambda-client/lambda?color=lightcoral&label=lines%20of%20code)