build(deps): update dependency org.sonatype.plugins:nexus-staging-maven-plugin to v1.6.9 (#612)

[![WhiteSource Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| org.sonatype.plugins:nexus-staging-maven-plugin | `1.6.8` -> `1.6.9` | [![age](https://badges.renovateapi.com/packages/maven/org.sonatype.plugins:nexus-staging-maven-plugin/1.6.9/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/org.sonatype.plugins:nexus-staging-maven-plugin/1.6.9/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/org.sonatype.plugins:nexus-staging-maven-plugin/1.6.9/compatibility-slim/1.6.8)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/org.sonatype.plugins:nexus-staging-maven-plugin/1.6.9/confidence-slim/1.6.8)](https://docs.renovatebot.com/merge-confidence/) |

---

### Configuration

📅 **Schedule**: At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Renovate will not automatically rebase this PR, because other commits have been found.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click this checkbox.

---

This PR has been generated by [WhiteSource Renovate](https://renovate.whitesourcesoftware.com). View repository job log [here](https://app.renovatebot.com/dashboard#github/googleapis/java-tasks).

Author: renovate-bot

tasks/pom.xml

@@ -46,7 +46,7 @@
       <plugin>
         <groupId>org.sonatype.plugins</groupId>
         <artifactId>nexus-staging-maven-plugin</artifactId>
-        <version>1.6.8</version>
+        <version>1.6.9</version>
         <configuration>
           <skipNexusStagingDeployMojo>true</skipNexusStagingDeployMojo>
         </configuration>