fix: samples/client/petstore/java/webclient-swagger2/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-IOPROJECTREACTORNETTY-10770514

Author: snyk-bot

samples/client/petstore/java/webclient-swagger2/pom.xml

@@ -129,7 +129,7 @@
         <jackson-version>2.17.1</jackson-version>
         <jackson-databind-version>2.17.1</jackson-databind-version>
         <jackson-databind-nullable-version>0.2.6</jackson-databind-nullable-version>
-        <spring-boot-version>2.7.17</spring-boot-version>
+        <spring-boot-version>3.3.7</spring-boot-version>
         <jakarta-annotation-version>1.3.5</jakarta-annotation-version>
         <reactor-version>3.4.34</reactor-version>
         <reactor-netty-version>1.0.39</reactor-netty-version>