CPP: Change note.

change-notes/1.22/analysis-cpp.md

@@ -11,6 +11,7 @@
 
 | **Query**                  | **Expected impact**    | **Change**                                                       |
 |----------------------------|------------------------|------------------------------------------------------------------|
+| Expression has no effect (`cpp/useless-expression`) | Fewer false positive results | Calls to functions with the `weak` attribute are no longer considered to be side effect free, because they could be overridden with a different implementation at link time. |
 | Suspicious pointer scaling (`cpp/suspicious-pointer-scaling`) | Lower precision | The precision of this query has been reduced to "medium". This coding pattern is used intentionally and safely in a number of real-world projects. Results are no longer displayed on LGTM unless you choose to display them. |
 
 ## Changes to QL libraries