This is instruction how to remove Read more button from post grid.
It require modification of post grid element but it is pretty easy.
First go and edit your site, where you have your post grid and you have to clone current Grid element template
It will open new tab with grid element to edit. Remove button, give some name to template and save it.
Next get back to editing your site, refresh it
, and while editing post grid, in Item design
chose your new created template.
With kind regards.