Register a dispatcher for str8. (This makes test_copy.py pass again.)

Make registeration of str dispatcher unconditional.
diff --git a/Lib/copy.py b/Lib/copy.py
index cba83c1..d5a7153 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -184,12 +184,9 @@
     d[complex] = _deepcopy_atomic
 except NameError:
     pass
+d[str8] = _deepcopy_atomic
 d[str] = _deepcopy_atomic
 try:
-    d[str] = _deepcopy_atomic
-except NameError:
-    pass
-try:
     d[types.CodeType] = _deepcopy_atomic
 except AttributeError:
     pass