Bump com.google.cloud.tools:jib-maven-plugin in /experimental/spring (#280)

Bumps [com.google.cloud.tools:jib-maven-plugin](https://github.com/GoogleContainerTools/jib) from 3.4.2 to 3.4.3.
- [Release notes](https://github.com/GoogleContainerTools/jib/releases)
- [Commits](https://github.com/GoogleContainerTools/jib/commits)

---
updated-dependencies:
- dependency-name: com.google.cloud.tools:jib-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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experimental/spring/spring-boot-nasp-example/pom.xml

@@ -35,7 +35,7 @@
             <plugin>
                 <groupId>com.google.cloud.tools</groupId>
                 <artifactId>jib-maven-plugin</artifactId>
-                <version>3.4.2</version>
+                <version>3.4.3</version>
                 <configuration>
                     <from>
                         <platforms>