fix: samples/client/echo_api/java/okhttp-gson-user-defined-templates/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-15365924

Author: snyk-bot

samples/client/echo_api/java/okhttp-gson-user-defined-templates/pom.xml

@@ -332,7 +332,7 @@
         <okhttp-version>4.12.0</okhttp-version>
         <gson-version>2.10.1</gson-version>
         <commons-lang3-version>3.18.0</commons-lang3-version>
-        <jackson-databind-nullable-version>0.2.7</jackson-databind-nullable-version>
+        <jackson-databind-nullable-version>0.2.10</jackson-databind-nullable-version>
         <jakarta-annotation-version>1.3.5</jakarta-annotation-version>
         <beanvalidation-version>2.0.2</beanvalidation-version>
         <junit-version>5.10.3</junit-version>