Editor: Fix register_block_type does not recognise ancestor block setting

When registering block through PHP, using `register_block_type` function, newly introduced `ancestor` block setting in `block.json` was not recognised. It worked though, when block is registered from JavaScript.

Props lovor, annezazu.
Fixes #56184.




git-svn-id: https://develop.svn.wordpress.org/trunk@53718 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/data/blocks/notice/block.json

@@ -4,7 +4,10 @@
 	"title": "Notice",
 	"category": "common",
 	"parent": [
-		"core/group"
+		"tests/group"
+	],
+	"ancestor": [
+		"tests/section"
 	],
 	"providesContext": {
 		"tests/message": "message"