README: Remove link to Travis CI

Author: sodabrew

README.md

@@ -3,8 +3,6 @@
 GitHub Actions
 [![GitHub Actions Status: Build](https://github.com/brianmario/mysql2/actions/workflows/build.yml/badge.svg)](https://github.com/brianmario/mysql2/actions/workflows/build.yml)
 [![GitHub Actions Status: Container](https://github.com/brianmario/mysql2/actions/workflows/container.yml/badge.svg)](https://github.com/brianmario/mysql2/actions/workflows/container.yml)
-Travis CI
-[![Travis CI Status](https://travis-ci.org/brianmario/mysql2.png)](https://travis-ci.org/brianmario/mysql2)
 Appveyor CI
 [![Appveyor CI Status](https://ci.appveyor.com/api/projects/status/github/sodabrew/mysql2)](https://ci.appveyor.com/project/sodabrew/mysql2)