ci: deprecate Travis CI

Author: umarcor

.travis.yml

@@ -7,7 +7,6 @@ Cobra is used in many Go projects such as [Kubernetes](http://kubernetes.io/),
 name a few. [This list](./projects_using_cobra.md) contains a more extensive list of projects using Cobra.
 
 [![](https://img.shields.io/github/workflow/status/spf13/cobra/Test?longCache=tru&label=Test&logo=github%20actions&logoColor=fff)](https://github.com/spf13/cobra/actions?query=workflow%3ATest)
-[![Build Status](https://travis-ci.org/spf13/cobra.svg "Travis CI status")](https://travis-ci.org/spf13/cobra)
 [![GoDoc](https://godoc.org/github.com/spf13/cobra?status.svg)](https://godoc.org/github.com/spf13/cobra)
 [![Go Report Card](https://goreportcard.com/badge/github.com/spf13/cobra)](https://goreportcard.com/report/github.com/spf13/cobra)
 [![Slack](https://img.shields.io/badge/Slack-cobra-brightgreen)](https://gophers.slack.com/archives/CD3LP1199)