Merge pull request #22381 from github/security-manager-legacy-fix

Update security manager beta note with info on legacy plans

Author: saritai

data/reusables/organizations/security-manager-beta-note.md

@@ -1,5 +1,5 @@
 {% note %}
 
-**Note:** The security manager role is in public beta and subject to change.
+**Note:** The security manager role is in public beta and subject to change. This feature is not available for organizations using legacy per-repository billing plans. 
 
 {% endnote %}