[Bug]: edge_gpt_free: broken image generation

[Andrej730]

Describe the bug | 简述

After cd411c2 ImageGen and ImageGenAsync classes were removed, but they are still used in the code for image generation:

gpt_academic/request_llms/edge_gpt_free.py

Lines 543 to 546 in d6bde0f

	async with ImageGenAsync("", True) as image_generator:
	images = await image_generator.get_images(
	response["arguments"][0]["messages"][0]["text"],
	)

gpt_academic/request_llms/edge_gpt_free.py

Lines 1032 to 1036 in d6bde0f

	image_generator = ImageGen(Cookie.image_token)
	image_generator.save_images(
	image_generator.get_images(self.prompt),
	output_dir=self.image_dirpath,
	)