fix: Add comma between bigquery requirements listings

[madison-ookla]

Summary of Changes

This PR fixes an issue wherein this package could not be installed with the bigquery extra because a comma was missing between two package specifications. Python allows this as a multi-line string, so both requirements are concatenated and neither can be found.

Resolves amundsen-io/amundsen#938

Tests

No tests were modified

Documentation

No documentation needed to be changed, this was a change to align with expected behavior.

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[feng-tao]

lgtm, could you fix the DCO? thanks