message: core: fix elided lifetime clippy lint in test
diff: @@ -501,9 +501,9 @@ mod tests {
  let linked_list = LinkedList::new();
  - fn expect<'a>(
  - callsites: &'a mut impl Iterator<Item = &'static Registration>,
  - ) -> impl FnMut(&'static Registration) + 'a {
  + fn expect(
  + callsites: &mut impl Iterator<Item = &'static Registration>,
  + ) -> impl FnMut(&'static Registration) + '_ {
  move |reg: &'static Registration| {
  let ptr = callsites
  .next()
  