Fixed a ReST error in cache docs.

The per-site cache

==================

**New in Django development version** (previous versions of Django only provided

a single ``CacheMiddleware`` instead of the two pieces described below).

**New in Django development version** (previous versions of Django only

provided a single ``CacheMiddleware`` instead of the two pieces described

below).

Once the cache is set up, the simplest way to use caching is to cache your

entire site. You'll need to add

``'django.middleware.cache.UpdateCacheMiddleware'`` and

``'django.middleware.cache.FetchFromCacheMiddleware' to your

``'django.middleware.cache.FetchFromCacheMiddleware'`` to your

``MIDDLEWARE_CLASSES`` setting, as in this example::

    MIDDLEWARE_CLASSES = (