Sorry 
What type of artifacts? When you zoom out so far that the shader is “struggling” to decide which pixel to draw so it skips a whole pixel row/column in the texture?
Why are you explicitly turning off mipmaps when loading the texture? Do you have a specific reason for it? That’s the first thing that could help you.
The third parameter has to be false to create mipmaps.
let texture = new BABYLON.Texture("https://i.imgur.com/clj2AYB.png", scene, false, true, BABYLON.Constants.TEXTURE_NEAREST_SAMPLINGMODE);
A solution if you wan to have an overall pixelated look is to use a postprocess: