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.

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

java/google/registry/export/CheckBackupAction.java

@@ -110,7 +110,7 @@ public class CheckBackupAction implements Runnable {
       throw e;
     } catch (Throwable e) {
       throw new InternalServerErrorException(
-          String.format("Exception occurred while checking datastore exports."), e);
+          "Exception occurred while checking datastore exports.", e);
     }
   }