Update test_wsgiref.py

Author: benediktjohannes

Lib/test/test_wsgiref.py

@@ -854,7 +854,7 @@ def testRaisesControlCharacters(self):
             with self.subTest(c0):
                 base = BaseHandler()
                 headers = Headers()
-                headers['key'] = f"val{c0}"
+                headers['key'] = f"val"
                 headers.add_header("key", "val")
                 # HTAB (\x09) is allowed in values, but not in names.
                 if c0 == "\t":