Fixes #37760

Description

#35892 introduced some changes to the Site Logo block, including an effect which was intended to discard any unsaved changes to the logo/icon if a user removes all their Site Logo blocks. This effect relied on getGlobalBlockCount to determine the existence of any Site Logo blocks, but does not work reliably in the Site Editor. If it fires erroneously, it breaks the Redo button. (See testing instructions).

This PR just removes that logic entirely in order to fix the Redo bug. Other options for discarding unsaved Site Logo changes can be explored separately at a much lower priority.

How has this been tested?

Verify you can reproduce the bug on trunk:

1. Load the Site Editor.
2. In the header template part, insert a Site Logo block and update the image.
3. Click into a different template part, which does not contain a Site Logo block. Insert any other block.
4. Click the "undo" button
5. Try to "redo" and notice the action is unavailable.

Now checkout this branch and repeat the testing instructions. This time, the "Redo" should be available and should re-insert the block removed by "Undo".

Screenshots

Types of changes

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).
• I've updated related schemas if appropriate.