ch-remote: reevaluate #[allow] attributes

Convert the still-needed #[allow] to #[expect] so it warns if the
lint stops firing.

Part of #8326.

Signed-off-by: Tushar Khatri <hello@tusharkhatri.in>

cloud-hypervisor/src/bin/ch-remote.rs

@@ -1232,7 +1232,7 @@ fn main() {
 
     if let Err(top_error) = target_api.do_command(&matches) {
         // Helper to join strings with a newline.
-        #[allow(clippy::needless_pass_by_value)]
+        #[expect(clippy::needless_pass_by_value)]
         fn join_strs(mut acc: String, next: String) -> String {
             if !acc.is_empty() {
                 acc.push('\n');