test: make unit test for nt-dml takes shorter time in favor of CI (#34888)
test: make unit test for nt-dml takes shorter time in favor of CI (#34888)

ref pingcap/tidb#33485
kyle-wang/tidb,ngaut/tidb,ngaut/tidb,c4pt0r/tidb,ngaut/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,kyle-wang/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,kyle-wang/tidb,pingcap/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,c4pt0r/tidb,kyle-wang/tidb,c4pt0r/tidb,kyle-wang/tidb,pingcap/tidb,kyle-wang/tidb