Update description for FeaturesUsed in LicenseUsageSummary documentation

Author: khalidabuhakmeh

src/content/docs/identityserver/reference/models/license-usage-summary.md

@@ -31,7 +31,7 @@ purposes.
 
 * **`FeaturesUsed`**
 
-  A `string` collection of issuers used with the current IdentityServer instance.
+  A `string` collection of features has been used since the IdentityServer instance ran.
 
 ## Using LicenseUsageSummary with .NET Lifetime Events