[1.11.x] Fixed #28548 -- Replaced 'middlewares' with 'middleware' in docs.

Backport of da3a5cee4f from master

docs/ref/contrib/flatpages.txt

@@ -147,7 +147,7 @@ can do all of the work.
 Note that the order of :setting:`MIDDLEWARE` matters. Generally, you can put
 :class:`~django.contrib.flatpages.middleware.FlatpageFallbackMiddleware` at the
 end of the list. This means it will run first when processing the response, and
-ensures that any other response-processing middlewares see the real flatpage
+ensures that any other response-processing middleware see the real flatpage
 response rather than the 404.
 
 For more on middleware, read the :doc:`middleware docs

docs/ref/request-response.txt

@@ -1039,7 +1039,7 @@ with the following notable differences:
 :class:`StreamingHttpResponse` should only be used in situations where it is
 absolutely required that the whole content isn't iterated before transferring
 the data to the client. Because the content can't be accessed, many
-middlewares can't function normally. For example the ``ETag`` and
+middleware can't function normally. For example the ``ETag`` and
 ``Content-Length`` headers can't be generated for streaming responses.
 
 Attributes