var d = app.activeDocument, MT= d.stories.everyItem().tables.everyItem().getElements();

for (j = 0; j< MT.length; j++)

for (k = 0; k< MT[j].rows.length; k++) {
row = MT[j].rows[k];
row.minimumHeight = row.height;
row.maximumHeight = row.height;
row.autoGrow = false;
}