#14832: 'first' now really refers to first arg in unittest assertItemsEqual

This appears to have been a mixup introduced when we switched from
'expected/actual' to 'first/second'.  The problem doesn't exist
in the corresponding assertCountEqual method in Python3.
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index 18dee02..f334b5b 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -872,7 +872,7 @@
             - [0, 1, 1] and [1, 0, 1] compare equal.
             - [0, 0, 1] and [0, 1] compare unequal.
         """
-        first_seq, second_seq = list(actual_seq), list(expected_seq)
+        first_seq, second_seq = list(expected_seq), list(actual_seq)
         with warnings.catch_warnings():
             if sys.py3kwarning:
                 # Silence Py3k warning raised during the sorting