Update lib/src/arg_parser_exception.dart

Co-authored-by: Nate Bosch <nbosch1@gmail.com>
diff --git a/lib/src/arg_parser_exception.dart b/lib/src/arg_parser_exception.dart
index dda5366..b1bdd25 100644
--- a/lib/src/arg_parser_exception.dart
+++ b/lib/src/arg_parser_exception.dart
@@ -9,7 +9,7 @@
   /// This will be empty if the error was on the root parser.
   final List<String> commands;
 
-  /// The argument that were being parsed when the error was discovered.
+  /// The argument name that was being parsed when the error was discovered.
   final String? arg;
 
   ArgParserException(super.message,