chore: remove duplicate code in WP_Theme_JSON_Gutenberg::get_block_nodes()

[justlevine]

What?

This PR removes a duplicate logical path for $include_node_paths_only inside WP_Theme_JSON_Gutenberg::get_block_nodes(), as this logic is already handled with a continue a few lines up in the loop spaghetti.

Why?

While this issue was surfaced by PHPStan (via #66693) it can be remediated independently as part of #66598

How?

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

Before	After

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Co-authored-by: justlevine <[email protected]>

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