Update CNCF sandbox acceptance in README.md (radius-project#7639)

# Description
PR updates text on Radius accepted as a CNCF sandbox project 
_Please explain the changes you've made._

## Type of change

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- This pull request is a minor refactor, code cleanup, test improvement,
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Fixes: #issue_number

Signed-off-by: Reshma Abdul Rahim <61033581+Reshrahim@users.noreply.github.com>
Co-authored-by: Karishma Chawla <kachawla@microsoft.com>

README.md

@@ -2,7 +2,7 @@
 
 Radius is a cloud-native application platform that enables developers and the platform engineers that support them to collaborate on delivering and managing cloud-native applications that follow organizational best practices for cost, operations and security, by default. Radius is an open-source project that supports deploying applications across private cloud, Microsoft Azure, and Amazon Web Services, with more cloud providers to come. 
 
-Radius has been submitted for consideration as a Cloud Native Computing Foundation (CNCF) [Sandbox project](https://github.com/cncf/sandbox/issues/65).
+Radius is a [Cloud Native Computing Foundation (CNCF) sandbox project](https://www.cncf.io/sandbox-projects/).
 
 ## Overview