fix typo (satwikkansal#107)

1f604 · satwikkansal · commit 64b310953a58 · 2018-12-07T00:24:45.000+05:30
diff --git a/README.md b/README.md
@@ -838,7 +838,7 @@ class C(A):
     pass
 ```
 
-**Ouptut:**
+**Output:**
 ```py
 >>> A.x, B.x, C.x
 (1, 1, 1)
