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/markdown_preview/src/markdown_preview_view.rs

@@ -132,7 +132,7 @@ impl MarkdownPreviewView {
                 workspace,
                 contents,
                 list_state,
-                tab_description: tab_description.into(),
+                tab_description: tab_description,
             }
         })
     }