Fix typo in comment

scrapy/core/downloader/handlers/http11.py

@@ -215,7 +215,7 @@ class ScrapyAgent(object):
             bodyproducer = None
             # Setting Content-Length: 0 even for POST requests is not a
             # MUST per HTTP RFCs, but it's common behavior, and some
-            # server require this otherwise returing HTTP 411
+            # servers require this, otherwise returning HTTP 411 Length required
             #
             # RFC 7230#section-3.3.2:
             # "a Content-Length header field is normally sent in a POST