Update URL to final version of docs in ExternalRefType.md

[bact]

• CISA Secure Software Development Attestation Form

  • Update URL: https://www.cisa.gov/sites/default/files/2023-04/secure-software-self-attestation_common-form_508.pdf -> https://www.cisa.gov/resources-tools/resources/secure-software-development-attestation-form
  • The current URL points to a draft version. The new URL is the final version.

• NIST SP 800-218

  • Update URL: https://csrc.nist.gov/publications/detail/sp/800-218/final -> https://csrc.nist.gov/pubs/sp/800/218/final
  • Update text label: "Secure Software Development Framework (SSDF)" -> "Secure Software Development Framework (SSDF) Version 1.1"

• NIST SP 800-161

  • Update URL: https://csrc.nist.gov/publications/detail/sp/800-161/rev-1/final -> https://csrc.nist.gov/pubs/sp/800/161/r1/final

• NTIA VEX one-page summary

  • Update text label: "NTIA VEX one-page" -> "NTIA VEX one-page summary"

[kestewart]

Thanks for catching this!