message: utils: Use explicit `u64::from`
  Prep for a PR which may pull in the `glib` crate which has
  a conflicting impl for this conversion (which is likely a bug).
diff: @@ -217,7 +217,7 @@ mod tests {
  Err(_) => Duration::from_secs(1),
  };
  prop_assert!(res.as_secs() > 0);
  - prop_assert!((res.as_secs() / 60) < MAX_WEEKLY_MINS.into());
  + prop_assert!((res.as_secs() / 60) < u64::from(MAX_WEEKLY_MINS));
  }
  #[test]
  