deps: update dependency com.google.cloud:google-cloud-monitoring to v3.18.0 (#2426)

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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/google-cloud-java) | `3.17.0` -> `3.18.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.18.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.18.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.18.0/compatibility-slim/3.17.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-monitoring/3.18.0/confidence-slim/3.17.0)](https://docs.renovatebot.com/merge-confidence/) |

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samples/install-without-bom/pom.xml

@@ -23,7 +23,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <opencensus.version>0.31.1</opencensus.version>
     <trace.version>2.17.0</trace.version>
-    <cloudmonitoring.version>3.17.0</cloudmonitoring.version>
+    <cloudmonitoring.version>3.18.0</cloudmonitoring.version>
   </properties>
 
 

samples/snapshot/pom.xml

@@ -23,7 +23,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <opencensus.version>0.31.1</opencensus.version>
     <trace.version>2.17.0</trace.version>
-    <cloudmonitoring.version>3.17.0</cloudmonitoring.version>
+    <cloudmonitoring.version>3.18.0</cloudmonitoring.version>
   </properties>
 
   <dependencies>