Fix README CERT-EU PDF links

[JSap0914]

Summary

• Update the two README CERT-EU PDF links that still use the old media.cert.europa.eu host.
• Keep the existing PDF paths and point them at cert.europa.eu, where both files are currently served.

Source proof

• Issue: Broken link : README.md #54 reports the README broken-links list, including both media.cert.europa.eu CERT-EU entries.
• Old host check: media.cert.europa.eu does not resolve in DNS from my environment.
• Replacement checks:
  • https://cert.europa.eu/static/WhitePapers/CERT-EU-SWP_14_005_v1_0.pdf returns HTTP 200, application/pdf.
  • https://cert.europa.eu/static/WhitePapers/TLP-WHITE-CERT-EU_Security_Guidance-22-001_v1_0.pdf returns HTTP 200, application/pdf.

Verification

• git diff --check
• curl -fsSI -L --max-time 20 for both replacement PDF URLs

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[Romeo-mz]

Hello @JSap0914 Thanks for tackling this issue. But I feem that we should fix all the broken links mentioned in the original issue #58 to cleanly close the PR/issue. Wdyt ?
Thanks !