chore(deps): update dependency com.google.cloud:google-cloud-monitoring to v3.0.3 (GoogleCloudPlatform#5909)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-monitoring](https://togithub.com/googleapis/java-monitoring) | `3.0.2` -> `3.0.3` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.0.3/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.0.3/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.0.3/compatibility-slim/3.0.2)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.0.3/confidence-slim/3.0.2)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v3.0.3`](https://togithub.com/googleapis/java-monitoring/blob/master/CHANGELOG.md#&#8203;303-httpswwwgithubcomgoogleapisjava-monitoringcomparev302v303-2021-09-01)

[Compare Source](https://togithub.com/googleapis/java-monitoring/compare/v3.0.2...v3.0.3)

</details>

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Author: renovate-bot

appengine-java8/bigquery/pom.xml

@@ -57,7 +57,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-monitoring</artifactId>
-      <version>3.0.2</version>
+      <version>3.0.3</version>
     </dependency>
 
     <dependency>