Update __init__.py to use the latest model (google-gemini#362)

* Update __init__.py

* Grammar

---------

Co-authored-by: Mark McDonald <macd@google.com>

Author: logankilpatrick

google/generativeai/__init__.py

@@ -30,8 +30,8 @@
 
 genai.configure(api_key=os.environ['API_KEY'])
 
-model = genai.GenerativeModel(name='gemini-pro')
-response = model.generate_content('Please summarise this document: ...')
+model = genai.GenerativeModel(name='gemini-1.5-flash')
+response = model.generate_content('Teach me about how an LLM works')
 
 print(response.text)
 ```