Edit the docs release plan (#47814)

Add an item to ensure that redirects only exist in the default version
of the docs. This is the version that we use to build the site map, and
links from the product and other Teleport sites only refer to
unversioned `/docs/` paths.

.github/ISSUE_TEMPLATE/test-plan-docs.md

@@ -36,11 +36,15 @@ to determine the rollout date.
     git submodule add https://github.com/gravitational/teleport content/<VERSION>.x
     ```
 
-## Is the docs site up to date with the new release?
+## Is the docs site content up to date with the new release?
 
 - [ ] Verify that Teleport version variables are correct and reflect the upcoming
   release. Check `docs/config.json` for this.
 
+- [ ] Ensure that redirects (as configured in `docs/config.json`) only exist for
+  the default version of the docs site, and have been removed from other
+  versions.
+
 - [ ] Remove version warnings in the docs that mention a version we no longer
   support _except_ for the last EOL version. E.g., if we no longer support
   version 10, remove messages saying "You need at least version n to use this