Reviews show on the details page through the Reviews tab, and GeoDirectory reviews are WordPress comments. You can hide the tab, turn reviews off for a whole post type, or keep comments and only remove the stars.
Remove the Reviews tab
Go to Places > Settings > Tabs, delete the Reviews item from the tab list and save. This still applies if your details page shows the tabs as a list down the page with [gd_single_tabs show_as_list="1"], because the list is built from the same tab settings. How to Use the Tabs Builder in GeoDirectory? explains the tab screen.
Turn off reviews for the whole post type
- Go to Places > Settings > General.
- Click Show Advanced.
- Tick Disable comments to stop reviews on every listing of that post type, or tick Disable ratings to keep comments but remove the review stars.
- Save.
Use the post type you need in place of Places, for example Events > Settings. To turn reviews off on single listings only, see How to Disable Comments on a Listing?.
Remove the rating stars from other places
Stars can also come from a [gd_post_rating] element in your details or archive item template. Edit the template page set at GeoDirectory > Settings > General > Pages and remove it there. There is no need to copy plugin template files to your child theme for this.