Python: Fix grammar in change note

Author: tausbn

python/ql/src/change-notes/2025-03-27-modernize-mixed-tuple-returns-query.md

@@ -2,4 +2,4 @@
 category: minorAnalysis
 ---
 
-- The `py/mixed-tuple-returns` query no longer flags instances where the tuple is passed into the function as an argument, as this lead to too many false positives.
+- The `py/mixed-tuple-returns` query no longer flags instances where the tuple is passed into the function as an argument, as this led to too many false positives.