Bump org.springframework.boot:spring-boot-starter-parent

Bumps [org.springframework.boot:spring-boot-starter-parent](https://github.com/spring-projects/spring-boot) from 3.2.2 to 4.0.3.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.2.2...v4.0.3)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-starter-parent
  dependency-version: 4.0.3
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

chapter4/knative-springboot/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
-    <version>3.4.1</version>
+    <version>4.0.4</version>
     <relativePath/>
   </parent>
   <groupId>com.example.events</groupId>