Fix doc comment in FixedDateTimeFormatter (#998)

pkgs/convert/lib/src/fixed_datetime_formatter.dart

diff --git a/pkgs/convert/lib/src/fixed_datetime_formatter.dart b/pkgs/convert/lib/src/fixed_datetime_formatter.dart
index 00b4838..957c07f 100644
--- a/pkgs/convert/lib/src/fixed_datetime_formatter.dart
+++ b/pkgs/convert/lib/src/fixed_datetime_formatter.dart
@@ -5,8 +5,8 @@
 /// A formatter and parser for [DateTime] in a fixed format [String] pattern.
 ///
 /// For example, calling
-/// `FixedDateTimeCodec('YYYYMMDDhhmmss').decodeToLocal('19960425050322')` has
-/// the same result as calling `DateTime(1996, 4, 25, 5, 3, 22)`.
+/// `FixedDateTimeFormatter('YYYYMMDDhhmmss').decode('19960425050322')` has
+/// the same result as calling `DateTime.utc(1996, 4, 25, 5, 3, 22)`.
 ///
 /// The allowed characters are
 /// * `Y`	for “calendar year”