Wrong link to Nextflow installation docs in pipeline template README

[drpatelh]

The Quick Start section of the main README in the pipeline template has the wrong link to the main NF installation docs. I could swear I changed this at some point to link to the main NF docs like I have in rnaseq/viralrecon but maybe not 🤷🏽

We will need to change the bump-versions code to deal with updating the version listed in that line too.

We currently have:

## Quick Start

1. Install [`Nextflow`](https://nf-co.re/usage/installation) (`>=21.04.0`)

But it needs to be:

## Quick Start

1. Install [`Nextflow`](https://www.nextflow.io/docs/latest/getstarted.html#installation) (`>=21.04.0`).