Small corrections to 1.3-alpha release notes (an unintended paragraph break,...

Small corrections to 1.3-alpha release notes (an unintended paragraph break, bad link, stray backtick, etc.).

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14523 bcc190cf-cafb-0310-a4f2-bffc1f526a37