Editor: Don't use fluid layout value in typography.

Changes fluid typography calculation to use fallback value if layout wide size is a fluid value.

Props ramonopoly, mukesh27, jastos, aurooba.
See #58754.


git-svn-id: https://develop.svn.wordpress.org/trunk@56503 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/data/themedir1/block-theme-child-with-fluid-layout/style.css

@@ -0,0 +1,8 @@
+/*
+Theme Name: Block Theme Child Theme With Fluid Layout
+Theme URI: https://wordpress.org/
+Description: For testing purposes only.
+Template: block-theme
+Version: 1.0.0
+Text Domain: block-theme-child-with-fluid-layout
+*/

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

@@ -0,0 +1,12 @@
+{
+	"version": 2,
+	"settings": {
+		"appearanceTools": true,
+		"layout": {
+			"wideSize": "clamp(1000px, 85vw, 2000px)"
+		},
+		"typography": {
+			"fluid": true
+		}
+	}
+}