deps: bump Spanner client to 6.81.2 (googleapis#1833)

Author: olavloite

pom.xml

@@ -61,7 +61,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-spanner-bom</artifactId>
-        <version>6.81.1</version>
+        <version>6.81.2</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>