[Sukhendu2002]

TinyMCE registers an unload listener when its selector engine switches to an iframe document. Chromium browsers deprecate or block this listener, producing console warnings when using the Classic block or Classic Editor.

Replace unload with pagehide in both tinymce.js and tinymce.min.js, preserving the callback that resets the selector engine’s document reference.

Update both revision headers and bump $tinymce_version to invalidate cached scripts.

Trac ticket: https://core.trac.wordpress.org/ticket/62924

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Used for: Focused browser verification, code review, and PR description drafting; final implementation and tests were reviewed and edited by me.

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