(node:34792) [DEP0066] DeprecationWarning: OutgoingMessage.prototype._headers is deprecated

Hi,
I get this message when I use the --http-redirects 1 option. Here is an example:

`node_modules/.bin/link-checker --http-always-get --http-redirects 1 --json test/`

``` raw
node --version
v14.6.0
```
