Fix red develop bb1f6fa20793

The merge lane found `develop` red at `bb1f6fa207939d44d5bf190053a238ca7f51b089` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `markdown-links-393-docs` The whole gate log: artifact `14858` on lane task 13032. Make `develop` pass its full gate again. Open a PR as usual: the merge lane merges a PR that fixes some of these and adds no failure even while `develop` is red.

Repointed the dead i18next plurals link (i18next.com returns 500 site-wide) at its GitHub doc source, which fixes the markdown-links stage. Quick gate green; PR #7820 queued in the merge lane. Memory: none applied.