Update functional test

Author: zenlyj

tests/functional/u/used/used_before_assignment_postponed_evaluation.py

@@ -20,7 +20,7 @@ def f():
     return datetime.datetime.now()  # [used-before-assignment]
 
 def g() -> datetime.datetime:
-    return datetime.datetime.now()  # FALSE NEGATIVE
+    return datetime.datetime.now()  # [used-before-assignment]
 
 if TYPE_CHECKING:
     class X:

tests/functional/u/used/used_before_assignment_postponed_evaluation.txt

@@ -1,2 +1,3 @@
 used-before-assignment:10:6:10:9::Using variable 'var' before assignment:INFERENCE
 used-before-assignment:20:11:20:19:f:Using variable 'datetime' before assignment:INFERENCE
+used-before-assignment:23:11:23:19:g:Using variable 'datetime' before assignment:INFERENCE