docs: update docstring for bigquery_create_routine sample

[pallabiwrites]

Fixed language issues.

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Fixes #<issue_number_goes_here> 🦕

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[shollyman]

Thanks for the contribution! Looks like we'll need a CLA to accept it, but looks fine otherwise.

[tswast]

@pallabiwrites are you able to sign the CLA? Otherwise we can't accept this contribution.

[pallabiwrites]

@pallabiwrites are you able to sign the CLA? Otherwise we can't accept this contribution.

Hi @tswast, I have already signed the CLA. Regards, Pallabi

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