BULK EDP Remove broken link in concept-zero-trust.md

Per User Story https://dev.azure.com/msft-skilling/Content/_workitems/edit/436781

The whitepaper does not appear to be posted on Microsoft anymore so link removal is the only option. However, there are these possible substitute links FYI:

- This security blog post discusses and links to the whitepaper: https://www.microsoft.com/en-us/security/blog/2021/05/05/how-to-apply-a-zero-trust-approach-to-your-iot-solutions/
- The link to the whitepaper from the security blog post goes to this URL: https://aka.ms/iot-zt-paper, which redirects to the following page (but this whitepaper isn't on it): https://azure.microsoft.com/en-us/resources/research/
- There is also this video: https://learn.microsoft.com/shows/internet-of-things-show/zero-trust-security-for-iot
- And this PDF from the Cloud Security Alliance: https://cloudsecurityalliance.org/artifacts/zero-trust-guidance-for-iot

Author: v-thepet

articles/defender-for-iot/organizations/concept-zero-trust.md

@@ -89,4 +89,3 @@ For more information, see:
 
 - [Azure user roles and permissions for Defender for IoT](roles-azure.md)
 - [Zero Trust Guidance Center](/security/zero-trust/zero-trust-overview)
-- White paper: [Zero Trust Cybersecurity for the Internet of Things](https://azure.microsoft.com/mediahandler/files/resourcefiles/zero-trust-cybersecurity-for-the-internet-of-things/Zero%20Trust%20Security%20Whitepaper_4.30_3pm.pdf)