fix link in changelog

Author: kosack

docs/changes/2921.bugfix.rst

@@ -1,4 +1,4 @@
 Fixed bug where units were incorrect in the output table of an
-`ctapipe.core.ExpressionEngine` if a table of class `astropy.table.Table` was
-passed to the call method. This bug did not affect calls using an
-`astropy.table.QTable`.
+:py:class:`ctapipe.core.feature_generator.FeatureGenerator <FeatureGenerator>`
+if a table of class `astropy.table.Table` was passed to the call method. This
+bug did not affect calls using an `astropy.table.QTable`.