AK: Remove unused JSON string APIs

Author: https://github.com/trflynn89
Commit: ee70f1327a
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3631
Reviewed-by: https://github.com/awesomekling ✅

AK/JsonArray.h

@@ -78,8 +78,6 @@ public:
     template<typename Builder>
     void serialize(Builder&) const;
 
-    [[nodiscard]] ByteString to_byte_string() const { return serialized<StringBuilder>(); }
-
     template<typename Callback>
     void for_each(Callback callback)
     {

AK/JsonValue.h

@@ -83,20 +83,6 @@ public:
     template<typename Builder>
     void serialize(Builder&) const;
 
-    ByteString as_string_or(ByteString const& alternative) const
-    {
-        if (is_string())
-            return as_string();
-        return alternative;
-    }
-
-    ByteString deprecated_to_byte_string() const
-    {
-        if (is_string())
-            return as_string();
-        return serialized<StringBuilder>();
-    }
-
     Optional<int> get_int() const { return get_integer<int>(); }
     Optional<i32> get_i32() const { return get_integer<i32>(); }
     Optional<i64> get_i64() const { return get_integer<i64>(); }