Pasting content shouldn't allow h1 tag for Rich Text editor

## Description

When pasting content from a document i.e. https://docs.google.com/document/d/1_J-Vb45O4WBAoK7H9uBMBUvQJ0SvJ8HAeLCEojJxql0/edit?tab=t.0

H1's get created this shouldn't be allowed as it's not an option in the editor itself

Start by locating the Rich Text editor and reproducing the issue by pasting content from a document such as the linked Google Doc. Trace the paste handling to see where an h1 is accepted, then verify that pasted content no longer creates h1 elements while the editor's available options remain unchanged.

Written by the indexing model from the issue text.