deps: update dependency com.google.cloud:google-cloud-pubsublite-parent to v1.6.3 (#336)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-pubsublite-parent](https://togithub.com/googleapis/java-shared-config) | `1.6.1` -> `1.6.3` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsublite-parent/1.6.3/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsublite-parent/1.6.3/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsublite-parent/1.6.3/compatibility-slim/1.6.1)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsublite-parent/1.6.3/confidence-slim/1.6.1)](https://docs.renovatebot.com/merge-confidence/) |

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pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <groupId>com.google.cloud</groupId>
     <artifactId>google-cloud-pubsublite-parent</artifactId>
-    <version>1.6.1</version>
+    <version>1.6.3</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.google.cloud</groupId>