V15 RC: Tiptap should only target valid block elements (#17712)

* fix: make sure we only target valid blocks

This is to say we should remove any invalid block elements to clean up the DOM. A block element is considered invalid if it does not have the `data-content-key` attribute.

* build(deps): bump tiptap from 2.10.2 to 2.10.3

this fixes a potential issue with link creations

* revert the 'leaf node specification'

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Co-authored-by: Niels Lyngsø <[email protected]>

Author: iOvergaard