bigquery: fix import path for context
bigquery: fix import path for context

goimports picked the stdlib import path for context for this file.

Change-Id: I422ffa1ac9f15767a640c35e2981785d32fad34e
Reviewed-on: https://code-review.googlesource.com/9630
Reviewed-by: Michael Darakananda <176c4818757ce942f02114959cee75d35f2575d9@google.com>
Reviewed-by: Sarah Adams <2b342d1c32491b4e7587e4a0e291a5f0f95d4167@google.com>
Reviewed-by: Chris Broadfoot <0c2851a4f8ab4aa5606e69c0757771dd13dbe686@google.com>

michael-grosshans/google-cloud-go,googleapis/google-cloud-go,michael-grosshans/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go