Revert "sum_tree: Replace rayon with futures (#41586) (#41846)

This causes the background executor to hang

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/remote_server/src/remote_editing_tests.rs

@@ -13,7 +13,7 @@ use fs::{FakeFs, Fs};
 use gpui::{AppContext as _, Entity, SemanticVersion, SharedString, TestAppContext};
 use http_client::{BlockedHttpClient, FakeHttpClient};
 use language::{
-    Buffer, FakeLspAdapter, LanguageConfig, LanguageMatcher, LanguageRegistry, LineEnding, Rope,
+    Buffer, FakeLspAdapter, LanguageConfig, LanguageMatcher, LanguageRegistry, LineEnding,
     language_settings::{AllLanguageSettings, language_settings},
 };
 use lsp::{CompletionContext, CompletionResponse, CompletionTriggerKind, LanguageServerName};
@@ -120,7 +120,7 @@ async fn test_basic_remote_editing(cx: &mut TestAppContext, server_cx: &mut Test
     // sees the new file.
     fs.save(
         path!("/code/project1/src/main.rs").as_ref(),
-        &Rope::from_str_small("fn main() {}"),
+        &"fn main() {}".into(),
         Default::default(),
     )
     .await
@@ -766,7 +766,7 @@ async fn test_remote_reload(cx: &mut TestAppContext, server_cx: &mut TestAppCont
 
     fs.save(
         &PathBuf::from(path!("/code/project1/src/lib.rs")),
-        &Rope::from_str_small("bangles"),
+        &("bangles".to_string().into()),
         LineEnding::Unix,
     )
     .await
@@ -781,7 +781,7 @@ async fn test_remote_reload(cx: &mut TestAppContext, server_cx: &mut TestAppCont
 
     fs.save(
         &PathBuf::from(path!("/code/project1/src/lib.rs")),
-        &Rope::from_str_small("bloop"),
+        &("bloop".to_string().into()),
         LineEnding::Unix,
     )
     .await