[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

docs/spelling_wordlist

@@ -476,7 +476,6 @@ metre
 MiB
 micrometre
 middleware
-middlewares
 migrationname
 millimetre
 Minification

docs/topics/i18n/translation.txt

@@ -2117,7 +2117,7 @@ To use ``LocaleMiddleware``, add ``'django.middleware.locale.LocaleMiddleware'``
 to your :setting:`MIDDLEWARE` setting. Because middleware order matters, follow
 these guidelines:
 
-* Make sure it's one of the first middlewares installed.
+* Make sure it's one of the first middleware installed.
 * It should come after ``SessionMiddleware``, because ``LocaleMiddleware``
   makes use of session data. And it should come before ``CommonMiddleware``
   because ``CommonMiddleware`` needs an activated language in order