message: syntax: update Unicode ages lookup
  This was a missed fix for the Unicode 12.1 update.
diff: @@ -365,6 +365,8 @@ fn ages(canonical_age: &str) -> Result<AgeIter> {
  ("V9_0", age::V9_0),
  ("V10_0", age::V10_0),
  ("V11_0", age::V11_0),
  + ("V12_0", age::V12_0),
  + ("V12_1", age::V12_1),
  ];
  assert_eq!(AGES.len(), age::BY_NAME.len(), "ages are out of sync");
  