Fix Theme buttons have correct visited style (#37343)

* Fixed an error when displaying visited buttons on the themes page on wp-admin

* changelog

* Fixed on load-themes

* Set a more specific CSS selector

* Moved the fix to its own function so that it is semantically correct

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/9061780177

Upstream-Ref: Automattic/jetpack@6eb0b61

src/features/wpcom-themes/css/ui-fixes.css

@@ -0,0 +1,3 @@
+.theme-browser .button:visited {
+	color: #fff;
+}

src/features/wpcom-themes/wpcom-themes.php

@@ -87,3 +87,16 @@ function wpcom_themes_remove_wpcom_actions() {
 	);
 }
 add_action( 'load-themes.php', 'wpcom_themes_remove_wpcom_actions' );
+
+/**
+ * Adds a CSS file to fix UI issues in the theme browser.
+ */
+function wpcom_themes_load_ui_fixes() {
+	wp_enqueue_style(
+		'wpcom-themes-ui-fixes',
+		plugins_url( 'css/ui-fixes.css', __FILE__ ),
+		array(),
+		Jetpack_Mu_Wpcom::PACKAGE_VERSION
+	);
+}
+add_action( 'load-themes.php', 'wpcom_themes_load_ui_fixes' );