Use async_maybe! instead of inline IIFEs (#6906)

This PR replaces instances where we were using an async IIFE with the
`async_maybe!` macro.

Release Notes:

- N/A

crates/zed/src/languages/css.rs

@@ -12,7 +12,7 @@ use std::{
     path::{Path, PathBuf},
     sync::Arc,
 };
-use util::ResultExt;
+use util::{async_maybe, ResultExt};
 
 const SERVER_PATH: &'static str =
     "node_modules/vscode-langservers-extracted/bin/vscode-css-language-server";
@@ -102,7 +102,7 @@ async fn get_cached_server_binary(
     container_dir: PathBuf,
     node: &dyn NodeRuntime,
 ) -> Option<LanguageServerBinary> {
-    (|| async move {
+    async_maybe!({
         let mut last_version_dir = None;
         let mut entries = fs::read_dir(&container_dir).await?;
         while let Some(entry) = entries.next().await {
@@ -124,7 +124,7 @@ async fn get_cached_server_binary(
                 last_version_dir
             ))
         }
-    })()
+    })
     .await
     .log_err()
 }