Update example in docstring

[kevinlacaille]

Usage in some docstrings haven't been updated to new syntax.

Orders API:

• OrdersClient
• create_order()

Data API:

• DataClient

Subscriptions API:

• No example given in docstring, need to add one

Expected behavior

async with Session() as sess:
    client = sess.client('orders')
    order = await client.create_order(request)

Actual behavior (describe the problem)

async with Session() as sess:
    cl = OrdersClient(sess)
    order = await cl.create_order(request)

Related Issues
N/A

Workaround
N/A

Minimum, Complete, Viable Code Sample
See expected behaviour.

Environment Information
N/A

Installation Method
N/A