chore(deps): update dependency com.google.cloud:google-cloud-spanner-jdbc to v2.28.0 (#1967)

Author: renovate-bot

samples/install-without-bom/pom.xml

@@ -29,7 +29,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-spanner-jdbc</artifactId>
-      <version>2.27.1</version>
+      <version>2.28.0</version>
     </dependency>
     <!-- [END spanner-jdbc_install_without_bom] -->