bpo-37412: Fix test_os.test_getcwd_long_path() on macOS (GH-14452)

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 2e73906..784000a 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -106,8 +106,7 @@
         dirname = dirname + ('a' * (dirlen - len(dirname)))
 
         with tempfile.TemporaryDirectory() as tmpdir:
-            with support.change_cwd(tmpdir):
-                path = tmpdir
+            with support.change_cwd(tmpdir) as path:
                 expected = path
 
                 while True: