[CI/infra] Front-matter params: place them under the `params` key

[chalin]

Since Hugo 0.123.0 custom params must be under the parms key in page front matter. Without it, we can get failures like https://github.com/open-telemetry/opentelemetry.io/actions/runs/12278556636/job/34260597540?pr=5758.

[chalin]

I re-read the Hugo docs and this isn't a requirement, but it does more cleanly separate concerns (and, I believe, reflect how things are managed internally).

[svrnm]

What about moving them out of the documents into the data folder? This way they would be much easier to reuse across the page?