Issue #27626: Spelling fixes in docs, comments and internal names

Based on patch by Ville Skyttä.
diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
index 3e88168..c81064d 100644
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -329,7 +329,7 @@
         d.clear()
         self.assertEqual(len(d), 0)
         self.assertEqual(list(d), [])
-        d.clear()               # clear an emtpy deque
+        d.clear()               # clear an empty deque
         self.assertEqual(list(d), [])
 
     def test_remove(self):