Docs: Remove `@summary` tags from JSDoc.

As decided in the JavaScript core chat. With a few reasons:

* It is visually cleaner when reading the source.
* This bring the JavaScript documentation closer to the PHP documentation.

The only disadvantage is that the JSDoc parser doesn't split out the summary and the description in the new format. We've decided to solve this when building the JavaScript documentation parser.

Props herregroen.
Fixes #42901.

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