docs(readme): remove broken tags

Author: apaparazzi0329

README.md

@@ -3,7 +3,6 @@
 [![Build and Test](https://github.com/watson-developer-cloud/node-sdk/workflows/Build%20and%20Test/badge.svg?branch=master)](https://github.com/watson-developer-cloud/node-sdk/actions?query=workflow%3A"Build+and+Test")
 [![Deploy and Publish](https://github.com/watson-developer-cloud/node-sdk/workflows/Deploy%20and%20Publish/badge.svg?branch=master)](https://github.com/watson-developer-cloud/node-sdk/actions?query=workflow%3A%22Deploy+and+Publish%22)
 [![codecov](https://codecov.io/gh/watson-developer-cloud/node-sdk/branch/master/graph/badge.svg)](https://codecov.io/gh/watson-developer-cloud/node-sdk)
-[![Slack](https://wdc-slack-inviter.mybluemix.net/badge.svg)](https://wdc-slack-inviter.mybluemix.net)
 [![npm-version](https://img.shields.io/npm/v/ibm-watson.svg)](https://www.npmjs.com/package/ibm-watson)
 [![npm-downloads](https://img.shields.io/npm/dm/ibm-watson.svg)](https://www.npmjs.com/package/ibm-watson)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)