Fix clippy::len_zero issues in fbcode/eden/scm/lib/indexedlog/src

Reviewed By: cjlongoria

Differential Revision: D90659994

fbshipit-source-id: 94d07003c3f49908d61ab69449b454d8cc791620

Author: generatedunixname89002005320881

eden/scm/lib/indexedlog/src/index.rs

@@ -1389,7 +1389,7 @@ impl MemKey {
 
     #[inline]
     fn is_unused(&self) -> bool {
-        self.key.len() == 0
+        self.key.is_empty()
     }
 }