It's probably an additional plugin which adds such an option to the game, since it's not part of the default RPG Maker MV.
I didn't see a v-sync plugin so far, but the monitor sync
pcnop also posted. It makes the game more fluid for people who have too high FPS. I made a test version with that plugin and a FPS counter, so that you can check if that helps, and if your FPS are at 60 or way higher usually. The "Synch Monitor FPS" option is disabled at start, and you have to activate it in the option menu.
Download: Mega
(This is not an update, and has no additional content since the last release. It's only a test version for the "FPS synch" plugin.)
I also found this plugin and was exporting the test version when I saw your post.