[BEAM-9481] Exclude signature files from expansion service test dependencies (#11093)
[BEAM-9481] Exclude signature files from expansion service test dependencies (#11093)

* Exclude signature files from test dependencies

* Apply suggestions from code review

Thanks Luke!

Co-Authored-By: Lukasz Cwik <a1559536771c19c1fd82195b5338c890b9c1c3e7@google.com>

Co-authored-by: Lukasz Cwik <a1559536771c19c1fd82195b5338c890b9c1c3e7@google.com>
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