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/editor/src/rust_analyzer_ext.rs

@@ -62,7 +62,6 @@ pub fn expand_macro_recursively(
             project
                 .read(cx)
                 .language_servers_for_buffer(buffer.read(cx), cx)
-                .into_iter()
                 .find_map(|(adapter, server)| {
                     if adapter.name.0.as_ref() == "rust-analyzer" {
                         Some((