fix: samples/client/petstore/java/okhttp-gson/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMSQUAREUPOKIO-5773320
- https://snyk.io/vuln/SNYK-JAVA-COMSQUAREUPOKIO-5820002
- https://snyk.io/vuln/SNYK-JAVA-ORGJETBRAINSKOTLIN-2393744

Author: snyk-bot

samples/client/petstore/java/okhttp-gson/pom.xml

@@ -336,7 +336,7 @@
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <gson-fire-version>1.9.0</gson-fire-version>
-        <okhttp-version>4.11.0</okhttp-version>
+        <okhttp-version>4.12.0</okhttp-version>
         <gson-version>2.10.1</gson-version>
         <commons-lang3-version>3.14.0</commons-lang3-version>
         <jackson-databind-nullable-version>0.2.6</jackson-databind-nullable-version>