Update certbot nginx+ssl configuration file source changes

[tmack8001]

Running the 2.x script ends with 2 files for certbot that have the following source showing that the curl request failed with a file not found.

curl -s https://raw.githubusercontent.com/certbot/certbot/master/certbot-nginx/certbot_nginx/tls_configs/options-ssl-nginx.conf
404: Not Found%

and

curl -s https://raw.githubusercontent.com/certbot/certbot/master/certbot/ssl-dhparams.pem
404: Not Found%

When this happens the nginx files aren't properly parsing these optional inclusions and the main script fails with this error for the end user:

Challenge failed for domain example.org
Challenge failed for domain www.example.org
http-01 challenge for example.org
http-01 challenge for www.example.org
Cleaning up challenges
Some challenges have failed.

IMPORTANT NOTES:
 - The following errors were reported by the server:

   Domain: example.org
   Type:   unauthorized
   Detail: Invalid response from
   https://example.org/.well-known/acme-challenge/JvUfqE5FQ8BRv-3dq1mjUiFMtSBUni-qD4I1AJuwqEU
   [137.117.17.70]: 404