General: Add a default `font-style` value for Adminbar links.

If a theme includes a `theme.json` file and sets a specific `font-style` on links, the font-style also changes the links in the WordPress admin bar, when the admin bar is visible on front-end. For example, this happens with the `pitch` style variation of Twenty Twenty-Three.

Using a default value for the `font-style` property prevents `theme.json` files from overriding it.

Props audrasjb, poena.
Fixes #56737.

Built from https://develop.svn.wordpress.org/trunk@54395


git-svn-id: http://core.svn.wordpress.org/trunk@53954 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/css/admin-bar-rtl.css

@@ -16,6 +16,7 @@ html {
 	font-size: 13px;
 	font-weight: 400;
 	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
+	font-style: normal;
 	line-height: 2.46153846;
 	border-radius: 0;
 	box-sizing: content-box;

wp-includes/css/admin-bar.css

@@ -15,6 +15,7 @@ html {
 	font-size: 13px;
 	font-weight: 400;
 	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
+	font-style: normal;
 	line-height: 2.46153846;
 	border-radius: 0;
 	box-sizing: content-box;

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-beta3-54394';
+$wp_version = '6.1-beta3-54395';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.