fix suffix

pkgs/yaml/lib/src/token.dart

diff --git a/pkgs/yaml/lib/src/token.dart b/pkgs/yaml/lib/src/token.dart
index 447e979..711950c 100644
--- a/pkgs/yaml/lib/src/token.dart
+++ b/pkgs/yaml/lib/src/token.dart
@@ -95,8 +95,8 @@
   /// The tag handle for named tags.
   final String? handle;
 
-  /// The tag suffix, or `null`.
-  final String? suffix;
+  /// The tag suffix.
+  final String suffix;
 
   TagToken(this.span, this.handle, this.suffix);