fix(core): unable to open block style select when in nested PTEs in fullscreen

[RitaDias]

Description

Fix issue where if you had nested PTEs you would not be able to open the block style dropdown

Before

https://github.com/sanity-io/sanity/assets/6951139/21ef9ef6-6de0-4ba5-b593-ea579fbf3fd5

What to review

The code makes sense, the tests make sense. Should we add some more tests? Thought about component but since the dropdown itself existed in the UI just had the "hidden" property I considered that the e2e was the best approach. Let me know if that is not correct

Testing

Tests are written You can also manually test on the All Bells and Whistles on the last PTE: content

Notes for release

Fixes issue where nested fullscreen PTEs were unable to open the block style dropdown