Change URL for CVE-2011-4121 to NVD

Updated CVE-2011-4121 YAML file to change the URL to the NVD.

Author: jasnow

rubies/ruby/CVE-2011-4121.yml

@@ -2,7 +2,7 @@
 engine: ruby
 cve: 2011-4121
 ghsa: mjg4-5rfj-952f
-url: https://github.com/advisories/GHSA-mjg4-5rfj-952f
+url: https://nvd.nist.gov/vuln/detail/CVE-2011-4121
 title: Private Ruby OpenSSL RSA key generation is always "1"
 date: 2019-11-26
 description: |