deps: update dependency com.google.cloud:google-cloud-storage to v2.15.0 (#2402)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-storage](https://togithub.com/googleapis/java-storage) | `2.14.0` -> `2.15.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-storage/2.15.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-storage/2.15.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-storage/2.15.0/compatibility-slim/2.14.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-storage/2.15.0/confidence-slim/2.14.0)](https://docs.renovatebot.com/merge-confidence/) |

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pom.xml

@@ -154,7 +154,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-storage</artifactId>
-        <version>2.14.0</version>
+        <version>2.15.0</version>
         <scope>test</scope>
       </dependency>
       <dependency>