Update breaking-change.yaml

Author: JamesNK

.github/ISSUE_TEMPLATE/breaking-change.yaml

@@ -25,6 +25,7 @@ body:
         - .NET 10 Preview 4
         - .NET 10 Preview 5
         - .NET 10 Preview 6
+        - .NET 10 Preview 7
         - .NET 10 RC 1
         - .NET 10 RC 2
         - .NET 10 GA