Remove unnecessary explicit generic type declarations

They can be inferred correctly even in Java 7, and display as
compiler warnings in IntelliJ.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173451087

java/google/registry/batch/DeleteContactsAndHostsAction.java

@@ -200,7 +200,7 @@ public class DeleteContactsAndHostsAction implements Runnable {
               new DeleteEppResourceReducer(),
               ImmutableList.of(
                   // Add an extra shard that maps over a null domain. See the mapper code for why.
-                  new NullInput<DomainBase>(),
+                  new NullInput<>(),
                   EppResourceInputs.createEntityInput(DomainBase.class)))));
     } catch (Throwable t) {
       logger.severefmt(t, "Error while kicking off mapreduce to delete contacts/hosts");

java/google/registry/batch/ExpandRecurringBillingEventsAction.java

@@ -113,7 +113,7 @@ public class ExpandRecurringBillingEventsAction implements Runnable {
             new ExpandRecurringBillingEventsReducer(isDryRun, persistedCursorTime),
             // Add an extra shard that maps over a null recurring event (see the mapper for why).
             ImmutableList.of(
-                new NullInput<Recurring>(),
+                new NullInput<>(),
                 createChildEntityInput(
                     ImmutableSet.<Class<? extends DomainResource>>of(DomainResource.class),
                     ImmutableSet.<Class<? extends Recurring>>of(Recurring.class))))));

java/google/registry/batch/MapreduceEntityCleanupUtil.java

@@ -168,7 +168,7 @@ class MapreduceEntityCleanupUtil {
    */
   private ImmutableSet<String> getPossibleIdsForPipelineJob(
       BaseDatastoreService datastore, String jobId) {
-    return getPossibleIdsForPipelineJobRecur(datastore, jobId, new HashSet<String>());
+    return getPossibleIdsForPipelineJobRecur(datastore, jobId, new HashSet<>());
   }
 
   /**

java/google/registry/batch/RefreshDnsOnHostRenameAction.java

@@ -139,7 +139,7 @@ public class RefreshDnsOnHostRenameAction implements Runnable {
               new RefreshDnsOnHostRenameReducer(refreshRequests, retrier),
               // Add an extra NullInput so that the reducer always fires exactly once.
               ImmutableList.of(
-                  new NullInput<DomainResource>(), createEntityInput(DomainResource.class)))));
+                  new NullInput<>(), createEntityInput(DomainResource.class)))));
     } catch (Throwable t) {
       logger.severefmt(t, "Error while kicking off mapreduce to refresh DNS for renamed hosts.");
     }