Fix changelog

Author: penelopeysm

HISTORY.md

@@ -8,6 +8,9 @@
 
 `DynamicPPL.TestUtils.AD.run_ad` now links the VarInfo by default.
 To disable this, pass the `linked=false` keyword argument.
+If the calculated value or gradient is incorrect, it also throws a `DynamicPPL.TestUtils.AD.ADIncorrectException` rather than a test failure.
+This exception contains the actual and expected gradient so you can inspect it if needed; see the documentation for more information.
+From a practical perspective, this means that if you need to add this to a test suite, you need to use `@test run_ad(...) isa Any` rather than just `run_ad(...)`.
 
 ### VarInfo constructors