Block Hooks: Fix child insertion next to Classic block #14337

Job	Run time
Core running from build / Core running from build / Linux	2m 15s
Core running from src / Core running from src / Linux	2m 4s
Core running from build / Core running from build / Windows	4m 0s
Core running from src / Core running from src / Windows	3m 34s
Core running from build / Core running from build / MacOS	2m 43s
Core running from src / Core running from src / MacOS	2m 56s
Gutenberg running from build / Gutenberg running from build / Linux	8m 42s
Gutenberg running from src / Gutenberg running from src / Linux	8m 41s
Gutenberg running from build / Gutenberg running from build / Windows	12m 11s
Gutenberg running from src / Gutenberg running from src / Windows	13m 27s
Gutenberg running from build / Gutenberg running from build / MacOS	9m 13s
Gutenberg running from src / Gutenberg running from src / MacOS	10m 34s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 20m 20s

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