Fix some issues caught by IntelliJ static code analysis

The most common issues were:
* Arrays.asList() shouldn't be called with a single parameter.
* Broken Javadoc @links.
* Unnecessary casts and type declarations.
* Unnecessary unused variable initializations.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=230994311

java/google/registry/model/ofy/AugmentedDeleter.java

@@ -60,7 +60,7 @@ abstract class AugmentedDeleter implements Deleter {
 
   @Override
   public Result<Void> key(Key<?> key) {
-    handleDeletion(Arrays.asList(key));
+    handleDeletion(ImmutableList.of(key));
     return delegate.keys(key);
   }