docs: Update README

PiperOrigin-RevId: 606818072

Author: yinghsienwu

vertexai/generative_models/README.md

@@ -38,18 +38,15 @@ print(model.generate_content("Why is sky blue?"))
 #### Using images and videos
 ```python
 from vertexai.preview.generative_models import GenerativeModel, Image
-print(vision_model = GenerativeModel("gemini-pro-vision"))
+vision_model = GenerativeModel("gemini-pro-vision")
 
 # Local image
 image = Image.load_from_file("image.jpg")
-print(vision_model.generate_content(image))
+print(vision_model.generate_content(["What is shown in this image?", image]))
 
 # Image from Cloud Storage
 image_part = generative_models.Part.from_uri("gs://download.tensorflow.org/example_images/320px-Felis_catus-cat_on_snow.jpg", mime_type="image/jpeg")
-print(vision_model.generate_content(image_part))
-
-# Text and image
-print(vision_model.generate_content(["What is shown in this image?", image]))
+print(vision_model.generate_content([image_part, "Describe this image?"]))
 
 # Text and video
 video_part = Part.from_uri("gs://cloud-samples-data/video/animals.mp4", mime_type="video/mp4")