Use native method for enumerating runes

DiscordChatExporter.Core/Discord/Data/Common/ImageCdn.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Globalization;
 using System.Linq;
-using DiscordChatExporter.Core.Utils.Extensions;
 
 namespace DiscordChatExporter.Core.Discord.Data.Common;
 
@@ -11,7 +10,7 @@ public static class ImageCdn
     // Standard emoji are rendered through Twemoji
     public static string GetStandardEmojiUrl(string emojiName)
     {
-        var runes = emojiName.GetRunes().ToArray();
+        var runes = emojiName.EnumerateRunes().ToArray();
 
         // Variant selector rune is skipped in Twemoji IDs,
         // except when the emoji also contains a zero-width joiner.

DiscordChatExporter.Core/Utils/Extensions/StringExtensions.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using System.Text;
 
 namespace DiscordChatExporter.Core.Utils.Extensions;
@@ -27,16 +26,6 @@ public static class StringExtensions
         return builder.ToString();
     }
 
-    public static IEnumerable<Rune> GetRunes(this string str)
-    {
-        var lastIndex = 0;
-        while (lastIndex < str.Length && Rune.TryGetRuneAt(str, lastIndex, out var rune))
-        {
-            yield return rune;
-            lastIndex += rune.Utf16SequenceLength;
-        }
-    }
-
     public static T? ParseEnumOrNull<T>(this string str, bool ignoreCase = true)
         where T : struct, Enum => Enum.TryParse<T>(str, ignoreCase, out var result) ? result : null;