Deprecate light_beam

BUR #14434 has been approved by @evazion.

deprecate light_beam

Ambiguous tag and the wiki already states it's an ambiguous

Previous topic #19330

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The bulk update request #14434 (forum #230464) has been rejected by @DanbooruBot.

The bulk update request #14434 (forum #230464) has been approved by @evazion.