chore(deps): update dependency com.google.cloud:google-cloud-spanner-jdbc to v1.21.0 (GoogleCloudPlatform#4854)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-spanner-jdbc](https://togithub.com/googleapis/java-spanner-jdbc) | `1.20.1` -> `1.21.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-jdbc/1.21.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-jdbc/1.21.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-jdbc/1.21.0/compatibility-slim/1.20.1)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-jdbc/1.21.0/confidence-slim/1.20.1)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/java-spanner-jdbc</summary>

### [`v1.21.0`](https://togithub.com/googleapis/java-spanner-jdbc/blob/master/CHANGELOG.md#&#8203;1210-httpswwwgithubcomgoogleapisjava-spanner-jdbccomparev1201v1210-2021-03-10)

[Compare Source](https://togithub.com/googleapis/java-spanner-jdbc/compare/v1.20.1...v1.21.0)

##### Features

-   add support for CommitStats ([#&GoogleCloudPlatform#8203;261](https://www.github.com/googleapis/java-spanner-jdbc/issues/261)) ([b32e7ae](https://www.github.com/googleapis/java-spanner-jdbc/commit/b32e7aebd4c8d24d052e4616b5dd7735878e01c3))
-   allow using UUID in PreparedStatement ([#&GoogleCloudPlatform#8203;365](https://www.github.com/googleapis/java-spanner-jdbc/issues/365)) ([4cbee6d](https://www.github.com/googleapis/java-spanner-jdbc/commit/4cbee6dcc2dfea2515437b55b0ecfc956205d739)), closes [#&GoogleCloudPlatform#8203;364](https://www.github.com/googleapis/java-spanner-jdbc/issues/364)

##### Dependencies

-   update dependency com.google.cloud:google-cloud-shared-dependencies to v0.20.1 ([#&GoogleCloudPlatform#8203;384](https://www.github.com/googleapis/java-spanner-jdbc/issues/384)) ([f0cdf11](https://www.github.com/googleapis/java-spanner-jdbc/commit/f0cdf117e20325601f1d1c13641267add5b39955))
-   update dependency com.google.cloud:google-cloud-spanner-bom to v5 ([#&GoogleCloudPlatform#8203;386](https://www.github.com/googleapis/java-spanner-jdbc/issues/386)) ([910c50c](https://www.github.com/googleapis/java-spanner-jdbc/commit/910c50c611cb30b96a2d5d0472afd2d8e3687013))

##### [1.20.1](https://www.github.com/googleapis/java-spanner-jdbc/compare/v1.20.0...v1.20.1) (2021-02-26)

##### Dependencies

-   update dependency com.google.cloud:google-cloud-shared-dependencies to v0.20.0 ([#&GoogleCloudPlatform#8203;374](https://www.github.com/googleapis/java-spanner-jdbc/issues/374)) ([398d886](https://www.github.com/googleapis/java-spanner-jdbc/commit/398d8864a72029a62b0a3adfaeafaeae76af3e1a))
-   update dependency com.google.cloud:google-cloud-spanner-bom to v4.0.2 ([#&GoogleCloudPlatform#8203;369](https://www.github.com/googleapis/java-spanner-jdbc/issues/369)) ([3a984c2](https://www.github.com/googleapis/java-spanner-jdbc/commit/3a984c26076f187a710b59c8487e330636319f7c))

</details>

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spanner/hibernate/pom.xml

@@ -37,7 +37,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-spanner-jdbc</artifactId>
-      <version>1.20.1</version>
+      <version>1.21.0</version>
     </dependency>
 
     <!-- Hibernate core dependency -->