README.md: update Travis badge (#22079)

The legacy dot-org URL was displaying a message about the repository
having migrated to the dot-com service, which now covers open-source
projects as well.

README.md

@@ -6,7 +6,7 @@ Official Golang implementation of the Ethereum protocol.
 https://camo.githubusercontent.com/915b7be44ada53c290eb157634330494ebe3e30a/68747470733a2f2f676f646f632e6f72672f6769746875622e636f6d2f676f6c616e672f6764646f3f7374617475732e737667
 )](https://pkg.go.dev/github.com/ethereum/go-ethereum?tab=doc)
 [![Go Report Card](https://goreportcard.com/badge/github.com/ethereum/go-ethereum)](https://goreportcard.com/report/github.com/ethereum/go-ethereum)
-[![Travis](https://travis-ci.org/ethereum/go-ethereum.svg?branch=master)](https://travis-ci.org/ethereum/go-ethereum)
+[![Travis](https://travis-ci.com/ethereum/go-ethereum.svg?branch=master)](https://travis-ci.com/ethereum/go-ethereum)
 [![Discord](https://img.shields.io/badge/discord-join%20chat-blue.svg)](https://discord.gg/nthXNEv)
 
 Automated builds are available for stable releases and the unstable master branch. Binary