clarify template purpose (#45191)

Author: Cam Soper

.github/ISSUE_TEMPLATE/02-breaking-change.yml

@@ -1,5 +1,5 @@
 name: ".NET breaking change"
-description: Report a change in .NET that breaks something that worked in a previous version. Intended mostly for product-team use.
+description: This template is for .NET product team members to report breaking changes to documentation content developers. Please report user-discovered issues in the appropriate product repo.
 title: "[Breaking change]: "
 labels:
   - breaking-change