Block Hooks: Fix child insertion next to Classic block #14278

Job	Run time
Core running from build / Core running from build / Linux	2m 11s
Core running from src / Core running from src / Linux	2m 1s
Core running from build / Core running from build / Windows	3m 52s
Core running from src / Core running from src / Windows	4m 12s
Core running from build / Core running from build / MacOS	2m 50s
Core running from src / Core running from src / MacOS	2m 39s
Gutenberg running from build / Gutenberg running from build / Linux	9m 0s
Gutenberg running from src / Gutenberg running from src / Linux	8m 45s
Gutenberg running from build / Gutenberg running from build / Windows	12m 38s
Gutenberg running from src / Gutenberg running from src / Windows	12m 17s
Gutenberg running from build / Gutenberg running from build / MacOS	7m 18s
Gutenberg running from src / Gutenberg running from src / MacOS	9m 56s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 17m 39s

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