Fix errors from rustc 1.71.0

Bug: 288268986
Test: m rust
Change-Id: If972c3856297978663642c60d162fcc504eb659d
diff --git a/keystore2/src/apc.rs b/keystore2/src/apc.rs
index 5d2083d..fbf9464 100644
--- a/keystore2/src/apc.rs
+++ b/keystore2/src/apc.rs
@@ -244,7 +244,7 @@
             // If cancelled by the user or if aborted by the client.
             (ResponseCode::CANCELLED, _, _) | (ResponseCode::ABORTED, true, _) => {
                 // Penalize.
-                let mut rate_info = state.rate_limiting.entry(uid).or_default();
+                let rate_info = state.rate_limiting.entry(uid).or_default();
                 rate_info.counter += 1;
                 rate_info.timestamp = start;
             }