Update SQLServer DDL script to drop sequences instead of tables

Resolves #4373

(cherry picked from commit 384b8a0)

Author: pranavjandu

spring-batch-core/src/main/resources/org/springframework/batch/core/schema-drop-sqlserver.sql

@@ -7,6 +7,6 @@ DROP TABLE  BATCH_JOB_EXECUTION_PARAMS;
 DROP TABLE  BATCH_JOB_EXECUTION;
 DROP TABLE  BATCH_JOB_INSTANCE;
 
-DROP TABLE  BATCH_STEP_EXECUTION_SEQ;
-DROP TABLE  BATCH_JOB_EXECUTION_SEQ;
-DROP TABLE  BATCH_JOB_SEQ;
+DROP SEQUENCE  BATCH_STEP_EXECUTION_SEQ;
+DROP SEQUENCE  BATCH_JOB_EXECUTION_SEQ;
+DROP SEQUENCE  BATCH_JOB_SEQ;