bpo-43907: add missing memoize call in pure python pickling of bytearray (GH-25501)

diff --git a/Lib/pickle.py b/Lib/pickle.py
index e63a8b6..5ab312f 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -818,6 +818,7 @@ def save_bytearray(self, obj):
             self._write_large_bytes(BYTEARRAY8 + pack("<Q", n), obj)
         else:
             self.write(BYTEARRAY8 + pack("<Q", n) + obj)
+        self.memoize(obj)
     dispatch[bytearray] = save_bytearray
 
     if _HAVE_PICKLE_BUFFER: