Bump com.google.cloud:google-cloud-spanner-jdbc from 2.14.6 to 2.15.1

Bumps [com.google.cloud:google-cloud-spanner-jdbc](https://github.com/googleapis/java-spanner-jdbc) from 2.14.6 to 2.15.1.
- [Release notes](https://github.com/googleapis/java-spanner-jdbc/releases)
- [Changelog](https://github.com/googleapis/java-spanner-jdbc/blob/main/CHANGELOG.md)
- [Commits](googleapis/java-spanner-jdbc@v2.14.6...v2.15.1)

---
updated-dependencies:
- dependency-name: com.google.cloud:google-cloud-spanner-jdbc
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -165,7 +165,7 @@
                 <dependency>
                     <groupId>com.google.cloud</groupId>
                     <artifactId>google-cloud-spanner-jdbc</artifactId>
-                    <version>2.14.6</version>
+                    <version>2.15.1</version>
                     <scope>runtime</scope>
                 </dependency>
             </dependencies>