LibWeb: Use StringView in CSS::PreferredColorScheme

This doesn't need to hold the string data.

Userland/Libraries/LibWeb/CSS/PreferredColorScheme.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -8,7 +8,7 @@
 
 namespace Web::CSS {
 
-PreferredColorScheme preferred_color_scheme_from_string(DeprecatedString const& value)
+PreferredColorScheme preferred_color_scheme_from_string(StringView value)
 {
     if (value.equals_ignoring_case("light"sv))
         return PreferredColorScheme::Light;

Userland/Libraries/LibWeb/CSS/PreferredColorScheme.h

@@ -1,12 +1,11 @@
 /*
- * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #pragma once
 
-#include <AK/DeprecatedString.h>
 #include <AK/StringView.h>
 
 namespace Web::CSS {
@@ -17,7 +16,7 @@ enum class PreferredColorScheme {
     Light,
 };
 
-PreferredColorScheme preferred_color_scheme_from_string(DeprecatedString const&);
+PreferredColorScheme preferred_color_scheme_from_string(StringView);
 StringView preferred_color_scheme_to_string(PreferredColorScheme);
 
 }