[hotfix][core][tests] Mark SerializerTestInstance with @Ignore

Some runners may attempt to run this class as a test.

flink-core/src/test/java/org/apache/flink/api/common/typeutils/SerializerTestInstance.java

@@ -21,11 +21,13 @@ package org.apache.flink.api.common.typeutils;
 
 import org.apache.flink.testutils.DeeplyEqualsChecker;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
+@Ignore
 public class SerializerTestInstance<T> extends SerializerTestBase<T> {
 
 	private final TypeSerializer<T> serializer;