[1.4.X] Fixed #18074 -- Fixed description of dumpdata command --database option.

Thanks aruseni for the report.

Backport of r17873 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.4.X@17874 bcc190cf-cafb-0310-a4f2-bffc1f526a37