Ignore send errors in installer (#6667)

## Summary

Similar to https://github.com/astral-sh/uv/pull/6182.

crates/uv-installer/src/installer.rs

@@ -94,7 +94,9 @@ impl<'a> Installer<'a> {
                 reporter,
                 relocatable,
             );
-            tx.send(result).unwrap();
+
+            // This may fail if the main task was cancelled.
+            let _ = tx.send(result);
         });
 
         rx.await