Enable clippy::unnecessary_filter_map (#8738)

This PR enables the
[`clippy::unnecessary_filter_map`](https://rust-lang.github.io/rust-clippy/master/index.html#/unnecessary_filter_map)
rule and fixes the outstanding violations.

Release Notes:

- N/A

crates/collab/src/db/queries/channels.rs

@@ -529,10 +529,7 @@ impl Database {
                 .all(&*tx)
                 .await?;
 
-            let channels = channels
-                .into_iter()
-                .filter_map(|channel| Some(Channel::from_model(channel)))
-                .collect();
+            let channels = channels.into_iter().map(Channel::from_model).collect();
 
             Ok(channels)
         })