Spurious dirty Rust change after running lint script (#20418)

Spurious dirty Rust change after running `poetry run ./scripts-dev/lint.sh`

Left behind from https://github.com/element-hq/synapse/pull/19996

changelog.d/20418.misc

@@ -0,0 +1 @@
+Run lint script over codebase to fix spurious dirty Rust change leftover from [#19996](https://github.com/element-hq/synapse/pull/19996).

rust/src/database/postgres/helpers.rs

@@ -160,7 +160,7 @@ mod tests {
 
     use std::pin::pin;
 
-    use futures::stream::{self, StreamExt};
+    use futures::stream::{self};
     use tokio::runtime::Runtime;
 
     use super::*;