README: fix broken badge
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<p align="center">
- <a href="https://github.com/liqotech/liqo/actions"><img src="https://github.com/liqotech/liqo/workflows/Go/badge.svg" alt="Integration Pipeline Status"></a>
+ <a href="https://github.com/liqotech/liqo/actions/workflows/integration.yml"><img src="https://github.com/liqotech/liqo/actions/workflows/integration.yml/badge.svg" alt="Integration Pipeline Status"></a>
<a href="https://goreportcard.com/report/github.com/liqotech/liqo"><img src=https://goreportcard.com/badge/github.com/liqotech/liqo></a>
<a href="https://coveralls.io/github/liqotech/liqo" alt="Liqo Test Coverage"><img src=https://coveralls.io/repos/github/liqotech/liqo/badge.svg?branch=master></a>
<a href="https://docs.liqo.io/en/stable" alt="Liqo's Documentation"><img src="https://readthedocs.org/projects/liqo/badge/"></a>
