QualitySettings.pixelLightCount

The maximum number of pixel lights that should affect any object.

If there are more lights illuminating an object, the dimmest ones will be rendered as vertex lights.

Use this from scripting if you want to have finer control than offered by quality settings levels.

JavaScripts

// Use at most one pixel light for every object

QualitySettings.pixelLightCount = 1;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
QualitySettings.pixelLightCount = 1;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
QualitySettings.pixelLightCount = 1