deps: update spanner.version to v1.52.0 (googleapis#95)

Author: renovate-bot

pom.xml

@@ -69,7 +69,7 @@
  <protobuf.version>3.11.4</protobuf.version>
  <threeten.version>1.4.1</threeten.version>
  <google.api-common.version>1.8.1</google.api-common.version>
- <spanner.version>1.51.0</spanner.version>
+ <spanner.version>1.52.0</spanner.version>
  <hamcrest.version>2.2</hamcrest.version>
  <error-prone.version>2.3.4</error-prone.version>
  <google.auth.version>0.20.0</google.auth.version>