Remove unused imports

Author: fmbenhassine

spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/Jackson2ExecutionContextStringSerializer.java

@@ -20,9 +20,7 @@
 import java.io.OutputStream;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;

spring-batch-core/src/test/java/org/springframework/batch/core/configuration/annotation/JobLoaderConfigurationTests.java

@@ -45,7 +45,6 @@
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.context.support.ApplicationObjectSupport;
 import org.springframework.lang.Nullable;
 
 /**