Clippy with the current stable toolchain (#6615)

Fix lints that are coming with rust 1.64

Passes with the earlier toolchain from `rust-toolchain.toml` as well.

crates/nu-command/src/network/fetch.rs

@@ -427,7 +427,7 @@ fn helper(
                     // primitive values ([key1 val1 key2 val2])
                     for row in table.chunks(2) {
                         if row.len() == 2 {
-                            custom_headers.insert(row[0].as_string()?, (&row[1]).clone());
+                            custom_headers.insert(row[0].as_string()?, row[1].clone());
                         }
                     }
                 }