fix(spanner): fix imports for doc samples (#10283)

* fix(spanner): fix imports for doc samples

* Update database-usage.rst

Co-authored-by: Christopher Wilcox <crwilcox@google.com>

docs/advanced-session-pool-topics.rst

@@ -10,7 +10,7 @@ contract laid out in
 
 .. code-block:: python
 
-   from google.cloud.spanner.pool import AbstractSessionPool
+   from google.cloud.spanner import AbstractSessionPool
 
    class MyCustomPool(AbstractSessionPool):
 
@@ -43,8 +43,7 @@ Create an instance of :class:`~google.cloud.spanner.pool.PingingPool`:
 
 .. code-block:: python
 
-   from google.cloud.spanner import Client
-   from google.cloud.spanner.pool import PingingPool
+   from google.cloud.spanner import Client, PingingPool
 
    client = Client()
    instance = client.instance(INSTANCE_NAME)
@@ -77,8 +76,7 @@ Create an instance of
 
 .. code-block:: python
 
-   from google.cloud.spanner import Client
-   from google.cloud.spanner.pool import TransactionPingingPool
+   from google.cloud.spanner import Client, TransactionPingingPool
 
    client = Client()
    instance = client.instance(INSTANCE_NAME)

docs/batch-usage.rst

@@ -132,7 +132,7 @@ rows do not cause errors.
 
 .. code:: python
 
-    from google.cloud.spanner.keyset import KeySet
+    from google.cloud.spanner import KeySet
 
     to_delete = KeySet(keys=[
         ('bharney@example.com',)
@@ -165,7 +165,7 @@ if the ``with`` block exits without raising an exception.
 
 .. code:: python
 
-    from google.cloud.spanner.keyset import KeySet
+    from google.cloud.spanner import KeySet
 
     client = spanner.Client()
     instance = client.instance(INSTANCE_NAME)

docs/client-usage.rst

@@ -13,8 +13,8 @@ and creating other objects:
 
 .. code:: python
 
-    from google.cloud import spanner_v1
-    client = spanner_v1.Client()
+    from google.cloud import spanner
+    client = spanner.Client()
 
 Long-lived Defaults
 -------------------
@@ -47,15 +47,15 @@ Configuration
 
   .. code::
 
-     >>> from google.cloud import spanner_v1
-     >>> client = spanner_v1.Client()
+     >>> from google.cloud import spanner
+     >>> client = spanner.Client()
 
   or pass in ``credentials`` and ``project`` explicitly
 
   .. code::
 
-     >>> from google.cloud import spanner_v1
-     >>> client = spanner_v1.Client(project='my-project', credentials=creds)
+     >>> from google.cloud import spanner
+     >>> client = spanner.Client(project='my-project', credentials=creds)
 
 .. tip::
 

docs/database-usage.rst

@@ -230,7 +230,7 @@ contract laid out in :class:`~google.cloud.spanner.pool.AbstractSessionPool`:
 
 .. code-block:: python
 
-   from google.cloud.pool import AbstractSessionPool
+   from google.cloud.spanner import AbstractSessionPool
 
    class MyCustomPool(AbstractSessionPool):