Fix deserialization issue. (#4795)

* Previous released broke the API under the assumption that we were always sending Optional.empty before.
* But then we pushed the wrong version, so pushing an Optional.of.

changelog/@unreleased/pr-4795.v2.yml

@@ -0,0 +1,6 @@
+type: improvement
+improvement:
+  description: |-
+    Fix deserialization issue.
+  links:
+  - https://github.com/palantir/atlasdb/pull/4795

lock-api-objects/src/main/java/com/palantir/lock/watch/NoOpLockWatchEventCache.java

@@ -26,7 +26,6 @@
 public class NoOpLockWatchEventCache implements LockWatchEventCache {
     public static final LockWatchEventCache INSTANCE = new NoOpLockWatchEventCache();
     private static final IdentifiedVersion FAKE = ImmutableIdentifiedVersion.of(UUID.randomUUID(), 0L);
-    private static final Optional<IdentifiedVersion> FAKE_OPTIONAL_VERSION = Optional.of(FAKE);
     private static final TransactionsLockWatchEvents NONE = TransactionsLockWatchEvents.failure(
             LockWatchStateUpdate.snapshot(UUID.randomUUID(), -1L, ImmutableSet.of(), ImmutableSet.of()));
 
@@ -36,7 +35,7 @@ private NoOpLockWatchEventCache() {
 
     @Override
     public Optional<IdentifiedVersion> lastKnownVersion() {
-        return FAKE_OPTIONAL_VERSION;
+        return Optional.empty();
     }
 
     @Override