[whatwg/url] Simplify the public suffix and registrable domain definitions (PR #887)

As of April 1, 2025, the Public Suffix List algorithm was modified so that the trailing dot of a domain would be retained in the result. Quotes from [this algorithm](https://github.com/publicsuffix/list/wiki/Format#formal-algorithm):

> * The public suffix is the set of labels from the domain which match the labels of the prevailing rule, using the matching algorithm above. A trailing dot shall be added if the domain included one. (See Note 3)

>  **Note 3**
> Callers of the algorithm often cannot determine if the domain to be queried is an FQDN but may treat `example.com` and `example.com.` as distinct. To support this, the algorithm should retain that distinction. This means looking up `example.com` should yield `com` while looking up `example.com.` should yield `com.` as the public suffix.

Therefore, there is no need to add a trailing dot to the result if the input domain has one, as this is done by the PSL algorithm.

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You can view, comment on, or merge this pull request online at:

  https://github.com/whatwg/url/pull/887

-- Commit Summary --

  * Simplify the public suffix and registrable domain definitions

-- File Changes --

    M url.bs (20)

-- Patch Links --

https://github.com/whatwg/url/pull/887.patch
https://github.com/whatwg/url/pull/887.diff

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