chore: fix lint failures in spanner samples (#17176)

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Fixes #<issue_number_goes_here> 🦕

Author: sakthivelmanii

packages/google-cloud-spanner/samples/samples/archived/backup_snippet_test.py

@@ -18,6 +18,7 @@
 from google.api_core.exceptions import DeadlineExceeded
 from test_utils.retry import RetryErrors
 
+
 def unique_database_id():
     """Creates a unique id for the database."""
     return f"test-db-{uuid.uuid4().hex[:10]}"

packages/google-cloud-spanner/samples/samples/autocommit_test.py

@@ -5,7 +5,6 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 from google.api_core.exceptions import Aborted
-import pytest
 from test_utils.retry import RetryErrors
 
 import autocommit

packages/google-cloud-spanner/samples/samples/conftest.py

@@ -33,6 +33,7 @@
     (exceptions.ResourceExhausted, exceptions.FailedPrecondition), max_tries=6, delay=15
 )
 
+
 @pytest.fixture(scope="module")
 def database_dialect():
     """Database dialect to be used for this sample.

packages/google-cloud-spanner/samples/samples/graph_snippets_test.py

@@ -80,6 +80,7 @@
                     LABEL Transfers)
 """
 
+
 @pytest.fixture(scope="module")
 def database_dialect():
     """Spanner dialect to be used for this sample.

packages/google-cloud-spanner/samples/samples/quickstart_test.py

@@ -11,9 +11,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-import pytest
-
 import quickstart