Social Link: Rename mail to email

This makes the mail icon show if the user searches for mail or email.
The property value does not change, it stays as 'mail' so is still
compatibility with any existing social links.

The title change only allows it show up in search for both.

Fixes #21733

packages/block-library/src/social-link/variations.js

@@ -175,7 +175,7 @@ const variations = [
 	{
 		name: 'mail',
 		attributes: { service: 'mail' },
-		title: 'Mail',
+		title: 'Email',
 		icon: MailIcon,
 	},
 	{