deps: update dependency com.google.cloud:google-cloud-pubsub to v1.120.15 (#1475)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-pubsub](https://togithub.com/googleapis/java-pubsub) | `1.120.14` -> `1.120.16` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub/1.120.16/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub/1.120.16/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub/1.120.16/compatibility-slim/1.120.14)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub/1.120.16/confidence-slim/1.120.14)](https://docs.renovatebot.com/merge-confidence/) |

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samples/install-without-bom/pom.xml

@@ -59,7 +59,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-pubsub</artifactId>
-      <version>1.120.14</version>
+      <version>1.120.15</version>
       <scope>test</scope>
     </dependency>
   </dependencies>

samples/snapshot/pom.xml

@@ -59,7 +59,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-pubsub</artifactId>
-      <version>1.120.14</version>
+      <version>1.120.15</version>
       <scope>test</scope>
     </dependency>
   </dependencies>

samples/snippets/pom.xml

@@ -71,7 +71,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-pubsub</artifactId>
-      <version>1.120.14</version>
+      <version>1.120.15</version>
       <scope>test</scope>
     </dependency>
   </dependencies>