Replace noindex with rel=canonical

[tunetheweb]

For static sites:

Astro.url.hostname === 'httparchive.org'

Is evaluated at build time and so always is true. Meaning this is not reevaluated for staging sites and the like.

Let's use rel=canonical instead (which also covers production sites we don't want indexed like httparchive.web.app, wordpress.httparchive.org...etc).

[github-actions]

Visit the preview URL for this PR (updated for commit c023ae3):

https://httparchive--pr1341-tunetheweb-patch-1-nbqrke2v.web.app

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