deps: update dependency com.google.cloud:google-cloud-spanner-bom to v6.38.1 (#1162)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-spanner-bom](https://togithub.com/googleapis/java-spanner) | `6.38.0` -> `6.38.1` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.38.1/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.38.1/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.38.1/compatibility-slim/6.38.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.38.1/confidence-slim/6.38.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v6.38.1`](https://togithub.com/googleapis/java-spanner/blob/HEAD/CHANGELOG.md#&#8203;6381-httpsgithubcomgoogleapisjava-spannercomparev6380v6381-2023-03-29)

[Compare Source](https://togithub.com/googleapis/java-spanner/compare/v6.38.0...v6.38.1)

##### Dependencies

-   Update dependency com.google.cloud:google-cloud-shared-dependencies to v3.6.0 ([#&#8203;2352](https://togithub.com/googleapis/java-spanner/issues/2352)) ([19175ce](https://togithub.com/googleapis/java-spanner/commit/19175ce22777ac68f8c825a438c0a2503234aa42))

</details>

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Author: renovate-bot

pom.xml

@@ -62,7 +62,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-spanner-bom</artifactId>
-        <version>6.38.0</version>
+        <version>6.38.1</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>