Adding blended creds to known issues (#545)

Author: savitharaghunathan

docs/known_issues.md

@@ -1,3 +1,5 @@
 <h1 align="center">Known Issues</h1>
 
-- [[Documentation] Failed/PartiallyFailed Orphaned backup will not be removed by ObjectStorageSync](https://github.com/vmware-tanzu/velero/issues/4483)
+- [[Documentation] Failed/PartiallyFailed Orphaned backup will not be removed by ObjectStorageSync](https://github.com/vmware-tanzu/velero/issues/4483)
+
+- When using Azure as a provider, if the provider secret originally pointed to Service Principal credentials and then changed to use Storagekey Account credentials, it can create a blended view of credentials within the velero pod.