Update src/MarkItDown/Converters/TextileConverter.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: KSemenenko

src/MarkItDown/Converters/TextileConverter.cs

@@ -70,7 +70,7 @@ private static string ConvertToMarkdown(string textile)
             var headingMatch = Heading.Match(trimmed);
             if (headingMatch.Success)
             {
-                var level = int.Parse(headingMatch.Groups["level"].Value, System.Globalization.CultureInfo.InvariantCulture);
+                var level = int.Parse(headingMatch.Groups["level"].Value, CultureInfo.InvariantCulture);
                 builder.AppendLine(new string('#', Math.Clamp(level, 1, 6)) + " " + headingMatch.Groups["text"].Value.Trim());
                 continue;
             }