Enable clippy::useless_conversion (#8767)

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

Release Notes:

- N/A

crates/collab/src/tests/channel_tests.rs

@@ -1431,7 +1431,7 @@ fn assert_channels(
                 .ordered_channels()
                 .map(|(depth, channel)| ExpectedChannel {
                     depth,
-                    name: channel.name.clone().into(),
+                    name: channel.name.clone(),
                     id: channel.id,
                 })
                 .collect::<Vec<_>>()

crates/collab/src/tests/editor_tests.rs

@@ -833,7 +833,7 @@ async fn test_language_server_statuses(cx_a: &mut TestAppContext, cx_b: &mut Tes
     let mut fake_language_servers = client_a.language_registry().register_fake_lsp_adapter(
         "Rust",
         FakeLspAdapter {
-            name: "the-language-server".into(),
+            name: "the-language-server",
             ..Default::default()
         },
     );