Fix DH param generation

[dappnodedev]

This PR aims to fix the following bug:

Failed to reconfigure NGINX ShellError: Command failed: nginx -s reload
nginx: [emerg] PEM_read_bio_DHparams("/etc/ssl/dappnode/wildcard_certs/dhparam.pem") failed (SSL: error:0909006C:PEM routines:get_name:no start line:Expecting: DH PARAMETERS)

    at shell (/usr/src/app/build/utils/shell.js:56:19)
    at async reconfigureNGINX (/usr/src/app/build/api/utils/nginx.js:15:13)
    at async /usr/src/app/build/api/app.js:35:30 {
  cmd: 'nginx -s reload',
  killed: false,
  code: 1,
  signal: null,
  stdout: '',
  stderr: 'nginx: [emerg] PEM_read_bio_DHparams("/etc/ssl/dappnode/wildcard_certs/dhparam.pem") failed (SSL: error:0909006C:PEM routines:get_name:no start line:Expecting: DH PARAMETERS)\n'
}

It was caused due to /etc/ssl/dappnode/wildcard_certs/dhparam.pem being empty

[github-actions]

Dappnode bot has built and pinned the built packages to an IPFS node, for commit: 2798b79

This is a development version and should only be installed for testing purposes.

(by dappnodebot/build-action)