Editor: use layout.wideSize as max viewport width.

Use the value of `layout.wideSize` as the maximum viewport width for fluid font size calculations.

Props ramonopoly.

Fixes #58522.



git-svn-id: https://develop.svn.wordpress.org/trunk@55946 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/data/themedir1/block-theme-child-with-fluid-typography-config/theme.json

@@ -2,6 +2,9 @@
 	"version": 2,
 	"settings": {
 		"appearanceTools": true,
+		"layout": {
+			"wideSize": "1000px"
+		},
 		"typography": {
 			"fluid": {
 				"minFontSize": "16px"