Fix typo in google cloud example dag

[smowden]

False should not be passed as a string. It's correct in the other examples inside this file

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^ Add meaningful description above

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In case of fundamental code change, Airflow Improvement Proposal (AIP) is needed.
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[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst)
Here are some useful points:

• Pay attention to the quality of your code (flake8, pylint and type annotations). Our pre-commits will help you with that.
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[boring-cyborg]

Awesome work, congrats on your first merged pull request!