Bump google-cloud-nio from 0.123.2 to 0.123.7 (#609)

Bumps [google-cloud-nio](https://github.com/googleapis/java-storage-nio) from 0.123.2 to 0.123.7.
- [Release notes](https://github.com/googleapis/java-storage-nio/releases)
- [Changelog](https://github.com/googleapis/java-storage-nio/blob/master/CHANGELOG.md)
- [Commits](googleapis/java-storage-nio@v0.123.2...v0.123.7)

---
updated-dependencies:
- dependency-name: com.google.cloud:google-cloud-nio
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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spring-content-gcs/pom.xml

@@ -102,7 +102,7 @@
         <dependency>
             <groupId>com.google.cloud</groupId>
             <artifactId>google-cloud-nio</artifactId>
-            <version>0.123.2</version>
+            <version>0.123.7</version>
             <scope>test</scope>
         </dependency>
 	</dependencies>