statistics: fix two unstable tests (#27430)
statistics: fix two unstable tests (#27430)

 
ngaut/tidb,c4pt0r/tidb,pingcap/tidb,ngaut/tidb,kyle-wang/tidb,coocood/tidb,pingcap/tidb,c4pt0r/tidb,kyle-wang/tidb,ngaut/tidb,ngaut/tidb,pingcap/tidb,coocood/tidb,kyle-wang/tidb,kyle-wang/tidb,kyle-wang/tidb,c4pt0r/tidb,ngaut/tidb,c4pt0r/tidb,kyle-wang/tidb,pingcap/tidb,pingcap/tidb,ngaut/tidb,c4pt0r/tidb,pingcap/tidb,c4pt0r/tidb