The end result of this data being indexed confuses newbies and is the source of
an increasing number of invalid tickets in trac. More specifically:
1. User searches to find info on a specific feature.
2. Said feature in development version is backwards incompatible with previous
versions of Django.
3. User does not know better, assumes Django has a bug.
4. Invalid bug is filed in trac.
Hopefully, removing the dev documentation pages from search engines will help
solve this issue, since those who want to read the dev docs can just click
through to them by using the version navigation at the bottom of the docs