Disable caching 404 responses

This issue is based on the [comment](https://github.com/django/djangoproject.com/issues/2319#issuecomment-3541476664) about the release page link giving 404 error, which might be due to a caching issue. It probably needs some investigating to look into our caching mechanisms and if there are other improvements too.

Start by reproducing the release-page 404 described in the linked comment, then trace the project's caching mechanisms; no file or test is named in the issue. Confirm whether 404 responses are cached, determine the relevant entry point, and verify that the completed change prevents unwanted caching without breaking normal responses.

Written by the indexing model from the issue text.