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
+`ctapipe.core.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`.