Fix typo

Author: Tim Bruijnzeels

src/commons/eventsourcing/wal.rs

@@ -325,7 +325,7 @@ impl<T: WalSupport> WalStore<T> {
         // or archives all write-ahead log ("wal-") changes predating the new snapshot.
         //
         // It is fine if another thread gets the entity for this handle and updates it while we
-        // do do this. As it turns out, writing snapshots can be expensive for large objects, so
+        // do this. As it turns out, writing snapshots can be expensive for large objects, so
         // we do not want block updates while we do this.
         //
         // This function is intended to be called in the back-ground at regular (slow) intervals