Fix missing argument error in graphene example

[alibitek]

pip3 install graphene
python3 hello.py

An error occurred while resolving field Query.hello
Traceback (most recent call last):
  File "/home/alpha/.pyenv/versions/3.5.1/lib/python3.5/site-packages/graphql/execution/executor.py", line 190, in resolve_or_error
    return executor.execute(resolve_fn, source, args, context, info)
  File "/home/alpha/.pyenv/versions/3.5.1/lib/python3.5/site-packages/graphql/execution/executors/sync.py", line 7, in execute
    return fn(*args, **kwargs)
TypeError: resolve_hello() takes 3 positional arguments but 4 were given
None

Also see: https://github.com/graphql-python/graphene/#examples

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