chore: Prepare matrix-sdk-common for edition 2024

Cherry-picked some changes from cargo fix --edition.

Author: jplatte

crates/matrix-sdk-common/src/linked_chunk/relational.rs

@@ -369,7 +369,7 @@ where
     pub fn unordered_linked_chunk_items<'a>(
         &'a self,
         target: &OwnedLinkedChunkId,
-    ) -> impl 'a + Iterator<Item = (&'a Item, Position)> {
+    ) -> impl Iterator<Item = (&'a Item, Position)> + use<'a, ItemId, Item, Gap> {
         self.items.get(target).into_iter().flat_map(|items| {
             // Only keep items which have a position.
             items.values().filter_map(|(item, pos)| pos.map(|pos| (item, pos)))

crates/matrix-sdk-common/src/store_locks.rs

@@ -309,7 +309,7 @@ impl<S: BackingStore + Clone + SendOutsideWasm + 'static> CrossProcessStoreLock<
             let mut backoff = self.backoff.lock().await;
 
             let wait = match &mut *backoff {
-                WaitingTime::Some(ref mut val) => {
+                WaitingTime::Some(val) => {
                     let wait = *val;
                     *val = val.saturating_mul(2);
                     if *val >= max_backoff {