Loading old docs flashes `Go to v6.7` button before `Go to v7.1` button is rendered

1. Go to https://guides.emberjs.com/v3.14.0/templates/input-components/

See that the button to the new guides are rendered as `Go to v6.7` in a short flash before `Go to v7.1` is rendered (Video shows as first load, and reloads with `CMD+R`):

https://github.com/user-attachments/assets/732e4a8c-6209-464a-b83e-3472136776a8

Start by reproducing the flash at https://guides.emberjs.com/v3.14.0/templates/input-components/ and compare the initial and final navigation button labels shown in the attached video. Trace how the old guide page renders its link to the new guides, then verify that the page consistently shows `Go to v7.1` without first showing `Go to v6.7`.

Written by the indexing model from the issue text.