docs: Address security issue in example (#11532)

Author: pen4

docs/providers/openwhisk/examples/hello-world/java/pom.xml

@@ -10,7 +10,7 @@
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <maven.compiler.source>1.8</maven.compiler.source>
  <maven.compiler.target>1.8</maven.compiler.target>
- <gson.version>2.8.2</gson.version>
+ <gson.version>2.8.9</gson.version>
  </properties>
  <dependencies>
  <dependency>