deps: update dependency com.google.cloud:google-cloud-spanner-bom to v5.1.0 (#393)

Author: renovate-bot

pom.xml

@@ -71,7 +71,7 @@
  <dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-spanner-bom</artifactId>
- <version>5.0.0</version>
+ <version>5.1.0</version>
  <type>pom</type>
  <scope>import</scope>
  </dependency>