Update README.md (brianc#2799)

Build status icon was still pointing at travis. We don't use travis anymore: we use github actions.

Author: brianc

README.md

@@ -1,6 +1,6 @@
 # node-postgres
 
-[![Build Status](https://secure.travis-ci.org/brianc/node-postgres.svg?branch=master)](http://travis-ci.org/brianc/node-postgres)
+![Build Status](https://github.com/brianc/node-postgres/actions/workflows/ci.yml/badge.svg)
 <span class="badge-npmversion"><a href="https://npmjs.org/package/pg" title="View this project on NPM"><img src="https://img.shields.io/npm/v/pg.svg" alt="NPM version" /></a></span>
 <span class="badge-npmdownloads"><a href="https://npmjs.org/package/pg" title="View this project on NPM"><img src="https://img.shields.io/npm/dm/pg.svg" alt="NPM downloads" /></a></span>