Migrate <p> to @wordpress/ui Text in Layout Constraint Helptext

[saranshsinhaa]

What?

Part of: #77265

Why?

Now that the required tooling is in place, we can start applying consistent text styling across the site and block editor. This can be done by replacing instances of __experimentalText and __experimentalHeading, as well as any ad hoc styled text, with the Text component from the UI package.

How?

Replaced the <p> with @wordpress/ui Text in Layout Constraint Helptext

Testing Instructions

1. Open the post editor.
2. Insert a block that exposes constrained layout controls (ex: Group).
3. Open Block settings and the Layout controls where Content width and Wide width appear.
4. Verify the helper sentence that appears under those controls: "Customize the width for all elements that are assigned to the center or wide columns." This sentence is the migrated text.

Before	After

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