I updated Minecraft to it's 1.16.1 version, and after entering my world I noticed that the blocks limits have black, orange and light blue lines; but in the Neather they weren't there.
I created a new world with his version and the lines were there too.
I uninstalled Minecraft and installed again, but the problem continues.
I don't have any mod or texture pack.
I opened 1.15.2 version and there were no lines, I downloaded the 1.16 version and the lines appeared.