README.md: change Tests badge to point to master (twbs#30765)

README.md

@@ -54,7 +54,7 @@ Read the [Getting started page](https://getbootstrap.com/docs/4.3/getting-starte
 ## Status
 
 [![Slack](https://bootstrap-slack.herokuapp.com/badge.svg)](https://bootstrap-slack.herokuapp.com/)
-[![Build Status](https://github.com/twbs/bootstrap/workflows/Tests/badge.svg)](https://github.com/twbs/bootstrap/actions?workflow=Tests)
+[![Build Status](https://github.com/twbs/bootstrap/workflows/Tests/badge.svg?branch=master)](https://github.com/twbs/bootstrap/actions?query=workflow%3ATests+branch%3Amaster)
 [![npm version](https://img.shields.io/npm/v/bootstrap.svg)](https://www.npmjs.com/package/bootstrap)
 [![Gem version](https://img.shields.io/gem/v/bootstrap.svg)](https://rubygems.org/gems/bootstrap)
 [![Meteor Atmosphere](https://img.shields.io/badge/meteor-twbs%3Abootstrap-blue.svg)](https://atmospherejs.com/twbs/bootstrap)