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/language/src/syntax_map.rs

@@ -766,7 +766,7 @@ impl SyntaxSnapshot {
         SyntaxMapCaptures::new(
             range.clone(),
             buffer.as_rope(),
-            self.layers_for_range(range, buffer).into_iter(),
+            self.layers_for_range(range, buffer),
             query,
         )
     }
@@ -780,7 +780,7 @@ impl SyntaxSnapshot {
         SyntaxMapMatches::new(
             range.clone(),
             buffer.as_rope(),
-            self.layers_for_range(range, buffer).into_iter(),
+            self.layers_for_range(range, buffer),
             query,
         )
     }