Bump spring-boot-starter-parent in /examples/webflux-undertow-java

Bumps [spring-boot-starter-parent](https://github.com/spring-projects/spring-boot) from 2.7.5 to 3.0.0.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.7.5...v3.0.0)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-starter-parent
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

examples/webflux-undertow-java/pom.xml

@@ -13,7 +13,7 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.7.5</version>
+        <version>3.0.0</version>
     </parent>
 
     <properties>