Update pom.xml to use latest client library.

Author: jsimonweb

spanner/cloud-client/pom.xml

@@ -128,7 +128,7 @@ limitations under the License.
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-bom</artifactId>
-        <version>0.34.0-alpha</version>
+        <version>0.37.0-alpha</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>