modify sql error (#12717)

dolphinscheduler-dao/src/main/resources/org/apache/dolphinscheduler/dao/mapper/ProcessTaskRelationMapper.xml

@@ -145,9 +145,7 @@
                 pre_task_code=#{processTaskRelation.preTaskCode},
                 pre_task_version=#{processTaskRelation.preTaskVersion}
             </set>
-            <where>
                 WHERE id = #{processTaskRelation.id}
-            </where>
         </foreach>
     </update>