DataGrid: fix ts issues in demos in strict mode (25_2)#32049

anna-shakhova wants to merge 2 commits intoDevExpress:25_2DevExpress/DevExtreme:25_2from

anna-shakhova:25_2__grid_demos_strict_tsanna-shakhova/DevExtreme:25_2__grid_demos_strict_tsCopy head branch name to clipboard