remove `getMockPlugins` override from IngestProcessorNotInstalledOnAllNodesIT & IngestClientIT

they didn't call the base class and it doesn't seem like they add something/the wrong way to solve a problem.

core/src/test/java/org/elasticsearch/ingest/IngestClientIT.java

@@ -43,7 +43,6 @@ import org.elasticsearch.test.ESIntegTestCase;
 
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
@@ -229,9 +228,4 @@ public class IngestClientIT extends ESIntegTestCase {
             assertThat(ex.getMessage(), equalTo("processor [test] doesn't support one or more provided configuration parameters [unused]"));
         }
     }
-
-    @Override
-    protected Collection<Class<? extends Plugin>> getMockPlugins() {
-        return Collections.singletonList(TestSeedPlugin.class);
-    }
 }

core/src/test/java/org/elasticsearch/ingest/IngestProcessorNotInstalledOnAllNodesIT.java

@@ -60,11 +60,6 @@ public class IngestProcessorNotInstalledOnAllNodesIT extends ESIntegTestCase {
         return installPlugin ? Arrays.asList(IngestTestPlugin.class) : Collections.emptyList();
     }
 
-    @Override
-    protected Collection<Class<? extends Plugin>> getMockPlugins() {
-        return Collections.singletonList(TestSeedPlugin.class);
-    }
-
     public void testFailPipelineCreation() throws Exception {
         installPlugin = true;
         String node1 = internalCluster().startNode();