Inaccurate description of version in go.mod

## Context

https://github.com/actions/setup-go/blob/6c1fd22b67f7a7c42ad9a45c0f4197434035e429/README.md?plain=1#L186

## Problem

A go.mod can contain a Go patch version. For example, see https://github.com/celestiaorg/celestia-app/blob/630a3e97a6bc7d34b792658f9080e3e5f0d027e8/go.mod#L3

## Proposal

Update the README.md