Fix warnings in preparation for Rust 1.54.0

This CL fixes several new warnings generated by rustc 1.54.0.

Bug: 194812675
Test: m rust
Change-Id: I3076313ea51c6f4e74029ad9fb45d6f0b6dea460
diff --git a/keystore2/src/gc.rs b/keystore2/src/gc.rs
index 2010c79..25f08c8 100644
--- a/keystore2/src/gc.rs
+++ b/keystore2/src/gc.rs
@@ -123,7 +123,7 @@
                     .super_key
                     .unwrap_key_if_required(&blob_metadata, &blob)
                     .context("In process_one_key: Trying to unwrap to-be-deleted blob.")?;
-                (self.invalidate_key)(&uuid, &*blob)
+                (self.invalidate_key)(uuid, &*blob)
                     .context("In process_one_key: Trying to invalidate key.")?;
             }
         }