Remove accidental duplicate lightcookie field from URP light preset editor

[arttu-peltonen]

Looks like the duplicate cookie field this was accidentally re-added after @martint-unity had removed it, probably a merge artifact. The Light Cookie field is now part of the Emission group.

Before this fix:

After this fix:

[github-actions]

Hi! This comment will help you figure out which jobs to run before merging your PR. The suggestions are dynamic based on what files you have changed.
Link to Yamato: https://unity-ci.cds.internal.unity3d.com/project/902/
Search for your PR branch using the search bar at the top, then add the following segment(s) to the end of the URL (you may need multiple tabs depending on how many packages you change)

URP
/jobDefinition/.yamato%252Fall-urp.yml%2523PR_URP_trunk
With changes to URP packages, you should also run
/jobDefinition/.yamato%252Fall-lightmapper.yml%2523PR_LightMapper_trunk

Depending on the scope of your PR, you may need to run more jobs than what has been suggested. Please speak to your lead or a Graphics SDET (#devs-graphics-automation) if you are unsure.

[martint-unity]

LGTM