chore: Prepare for Rust edition bump to 2024 (without autofix) (#27791)

Successor to #27779 - in this PR I've applied changes manually, without
futzing with if let lifetimes at all.

Release Notes:

- N/A

crates/channel/src/channel_chat.rs

@@ -183,7 +183,7 @@ impl ChannelChat {
 
         let channel_id = self.channel_id;
         let pending_id = ChannelMessageId::Pending(post_inc(&mut self.next_pending_message_id));
-        let nonce = self.rng.gen();
+        let nonce = self.rng.r#gen();
         self.insert_messages(
             SumTree::from_item(
                 ChannelMessage {
@@ -257,7 +257,7 @@ impl ChannelChat {
             cx,
         );
 
-        let nonce: u128 = self.rng.gen();
+        let nonce: u128 = self.rng.r#gen();
 
         let request = self.rpc.request(proto::UpdateChannelMessage {
             channel_id: self.channel_id.0,

crates/channel/src/channel_store.rs

@@ -824,7 +824,10 @@ impl ChannelStore {
         })
     }
 
-    pub fn remove_channel(&self, channel_id: ChannelId) -> impl Future<Output = Result<()>> {
+    pub fn remove_channel(
+        &self,
+        channel_id: ChannelId,
+    ) -> impl Future<Output = Result<()>> + use<> {
         let client = self.client.clone();
         async move {
             client